TWI874424B - RFID tags, plastic bottles and antennas - Google Patents

Abstract

An RFID tag is provided, comprising: an IC chip recording identification information; a loop conductor connected to the IC chip; and an antenna portion having two conductor portions connected to the loop conductor and extending from the loop conductor in directions separating from each other. The RFID tag is disposed on a surface of a container containing a liquid.

Description

RFID tags, plastic bottles and antennas

The present invention relates to a wireless radio frequency identification (RFID) tag, a plastic bottle and an antenna.

RFID tags to be attached to an attached object are becoming popular for logistics management and product management. RFID tags are tag stickers with RFID tags. RFID tags have an IC chip and an antenna electrically connected to the IC chip. RFID tags are also called wireless tags, IC tags, RF-ID tags, and RF tags. When the attached object to which such RFID tags are attached is a container for liquids such as a plastic bottle for beverages, it may hinder the reading of identification information. It is generally believed that the reason is that when there is an antenna near a liquid, the influence of the liquid will cause the characteristics of the antenna to change, and the radio waves will be absorbed by the liquid, etc.

Patent document 1 discloses an RFID tag sticker that can read identification information well even when a liquid that affects the reading of identification information is contained in an adhesive body. The RFID tag sticker disclosed in Patent document 1 has a structure in which an antenna protrudes from an adhesive body. As a result, the distance from the antenna to the liquid becomes longer, and the above-mentioned influence is reduced, so that the identification information stored in the RFID tag sticker can be read well.

[Prior Art Literature] (Patent Literature)

Patent document 1: Japanese Patent Application Publication No. 2006-277524

[The problem the invention is trying to solve]

However, the prior art disclosed in Patent Document 1 has a structure in which the antenna protrudes from the adhesive body, and therefore there is trouble such as the antenna being damaged during storage or transportation of the container, and there is still room for improvement.

The present invention is completed in view of the above content, and the problem to be solved is to obtain an RFID tag that can read identification information and will not cause troubles such as antenna damage caused by handling containers. [Technical means to solve the problem]

In order to solve the above problem, the RFID tag of the present invention is set on the surface of a container containing liquid, and the RFID tag has: an IC chip, which records identification information; a loop conductor, which is connected to the aforementioned IC chip; and an antenna part, which has two straight elements, which are straight-line conductors, which are connected to the aforementioned loop conductor and extend from the aforementioned loop conductor in a direction separated from each other, and are set to an electrical length of approximately λ/4 times the wavelength of the frequency used. (Effect of the invention)

According to the present invention, the following effects can be achieved: identification information can be read without causing troubles such as antenna damage caused by handling the container.

The embodiments of the present invention are described in detail with reference to the attached drawings. In the following description, the same symbols are attached to the common parts in the various figures and the description is omitted. In addition, for the convenience of understanding, the proportions of the components in the various figures may be different from the actual ones. In addition, in each form, deviations are allowed to the extent that the effects of the present invention are not impaired in parallel, right angles, horizontal, vertical, up and down, left and right, etc. In addition, the X-axis direction, the Y-axis direction and the Z-axis direction respectively represent the direction parallel to the X-axis, the direction parallel to the Y-axis and the direction parallel to the Z-axis. The X-axis direction, the Y-axis direction and the Z-axis direction are orthogonal to each other. The XY plane, the YZ plane, and the ZX plane represent an imaginary plane parallel to the X-axis direction and the Y-axis direction, an imaginary plane parallel to the Y-axis direction and the Z-axis direction, and an imaginary plane parallel to the Z-axis direction and the X-axis direction, respectively. In Figure 1 and thereafter, in the X-axis direction, the direction indicated by the arrow is the positive direction of the X-axis, and the direction opposite to the direction is the negative direction of the X-axis. In the Y-axis direction, the direction indicated by the arrow is the positive direction of the Y-axis, and the direction opposite to the direction is the negative direction of the Y-axis. In the Z-axis direction, the direction indicated by the arrow is the positive direction of the Z-axis, and the direction opposite to the direction is the negative direction of the Z-axis. The X-axis direction is equivalent to the height direction when viewing the container described later from the side. The Y-axis direction is equivalent to the width direction when viewing the container described later from the side. The Z-axis direction corresponds to the depth direction when a container described later is viewed from the side.

FIG. 1 is a perspective view of a container 300 containing a liquid 200 provided with an RFID tag 100 of an embodiment of the present invention. The container 300 shown in FIG. 1 is a container made of polyethylene terephthalate (PET bottle) containing the liquid 200. The liquid 200 is a liquid similar to water, such as a soda or mineral water. In addition, the liquid 200 is not limited thereto, and may also be oil, alcohol, etc. Furthermore, the liquid 200 may also be any mixture of water, oil, and alcohol (for example, water mixed with ethanol, etc.). A cover 301 is provided at the front end portion of the container 300 in the positive direction of the X-axis. The outer peripheral surface of the container 300 is covered with a transparent tape-shaped label sticker 302. The RFID tag 100 is provided on the label sticker 302. The RFID tag 100 exists in the air (in the atmosphere). That is, the environment around the container 300 in which the RFID tag 100 is installed is air.

In addition, the container 300 can be any container that can contain the liquid 200, for example, it can be a glass container, or it can be a sealed container such as Tupperware (registered trademark). In the following, for the sake of simplicity, the liquid 200 will be referred to as "liquid" and the container 300 will be referred to as "container". In addition, since the RFID tag 100 is provided with a dipole antenna, the RFID tag 100 is attached to the container 300 in a longitudinal manner, but the method of installing the RFID tag 100 on the container 300 is not limited to this.

Next, a configuration example of the RFID tag 100 will be described using FIG. 2. FIG. 2 is a diagram showing a configuration example of the RFID tag 100. The RFID tag 100 includes: a tape-shaped sheet 40; an IC chip 10 on which identification information is recorded; a loop conductor 20; and an antenna unit 30.

The sheet 40 is a film formed into a strip shape by laminating a plurality of synthetic resin films such as polyethylene terephthalate and polypropylene. The IC chip 10, the loop conductor 20 and the antenna unit 30 are arranged to be sandwiched between the plurality of laminated synthetic resin films. In addition, the IC chip 10, the loop conductor 20 and the antenna unit 30 can be directly set on the container body or on the label 302 of the container.

The IC chip 10 has an internal capacitor, and the inductance of the antenna portion 30 and the internal capacitor of the IC chip 10 form a matching circuit.

The loop conductor 20 is a conductive wiring pattern, and its shape is a loop (ring shape) with less than one turn when the sheet 40 is viewed from above along the Z-axis direction.

The loop conductor 20 is electrically connected to the IC chip 10 and the antenna unit 30. When the reader is used to read the identification information recorded in the IC chip 10, the antenna unit 30 receives the radio waves of the ultra-high frequency (UHF) band, such as the radio waves near 920 MHz, and the current flows in the loop conductor 20 by resonance. In this way, an electromotive force is generated to operate the IC chip 10. After the IC chip 10 is operated, the identification information recorded in the IC chip 10 is encoded by the IC chip 10, and the encoded data uses the radio waves near 920 MHz as a carrier wave and is wirelessly transmitted to a communication device such as a reader. The reader that receives the signal decodes the signal and transmits it to an external device. Thus, the RFID tag 100 of this embodiment is a passive radio wave type wireless tag without a power source (battery) for holding and transmitting identification information. Therefore, compared with an active wireless tag with a battery, the RFID tag 100 without a battery can be correspondingly miniaturized and low-priced.

The antenna section 30 is a dipole antenna configured to exhibit resonance characteristics with respect to the frequency of radio waves for wireless communication (e.g., the frequency of the UHF band) with the IC chip 10. The antenna section 30 has an electrical length that is approximately λ/2 (λ is the communication wavelength) as a whole.

The antenna portion 30 has a structure that can achieve impedance coherence matching with the IC chip 10, for example, with respect to radio waves of a frequency near 920 MHz (e.g., 860 MHz to 960 MHz, preferably 915 MHz to 935 MHz), even when the container 300 is filled with liquid and there is liquid near the antenna. The antenna portion 30 has two conductor portions (conductor portion 30A and conductor portion 30B) as a structure for achieving impedance coherence matching with the IC chip 10. The conductor portion 30A and the conductor portion 30B0 are conductive wiring patterns that are connected to the loop conductor 20 and extend from the loop conductor 20 in directions away from each other. The conductive wiring pattern can be formed by stamping and etching of copper foil and aluminum foil, by electroplating, by screen printing of metal paste, metal wire, and other conventional methods; however, it is formed by etching of aluminum here.

The conductor portion 30A and the conductor portion 30B are formed in line symmetry with respect to an imaginary line VL passing through the approximate center of the IC chip 10. The imaginary line VL is a line parallel to the XY plane and extending along the Y axis. The imaginary line VL is also a line that divides the area of the RFID tag 100 along the X axis into two equal parts.

The conductor part 30A and the conductor part 30B each have an electrical length equivalent to approximately λ/4 (λ is the communication wavelength). The impedance matching condition of the antenna part 30 is that the impedance when the signal source is observed from the load side and the impedance when the load is observed from the signal source side are in complex conjugate with each other. Therefore, if the signal source impedance Zs on the load side is Zs=Rs+jXs, when the load impedance Z1 is Zl=Rs-jXs, the maximum power is transmitted.

The conductor portion 30A and the conductor portion 30B are symmetrical with respect to the imaginary line VL, so the structure of the conductor portion 30A will be described below. The structure of the conductor portion 30B will be described in reverse with respect to the extension direction of the conductor portion 30A in the X-axis direction, and thus its description will be omitted.

The conductive portion 30A includes a first element 1 , a second element 2 , a third element 3 , and a fourth element 4 .

The first element 1 is a conductive wiring pattern in a zigzag shape extending from the loop conductor 20 toward the negative direction of the X axis. The first element 1 is a zigzag element.

The end of the first element 1 in the positive direction of the X-axis is connected to the loop conductor 20. The connection between the first element 1 and the loop conductor 20 is, for example, the peripheral portion of the loop conductor 20 on the positive direction side of the Y-axis. The first element 1 extends a certain distance from the connection with the loop conductor 20 at a specific angle (for example, 30° to 60°) relative to the negative direction of the X-axis, and further extends in the negative direction of the X-axis from the portion extending the certain distance. In addition, the shape of the first element 1 is not limited to the example shown in the figure, and may also be, for example, a shape that extends a certain distance from the connection with the loop conductor 20 relative to the positive direction of the Y-axis, bends vertically from the portion extending the certain distance, and extends in the negative direction of the X-axis.

The first element 1 is connected to the peripheral portion of the loop conductor 20 on the positive side of the Y axis, thereby narrowing the width of the entire antenna portion 30 in the X axis direction, and realizing an RFID tag 100 with a smaller ratio of longitudinal width to lateral width. Therefore, even when the RFID tag 100 is attached to a small-capacity plastic bottle with a small height in the X axis direction and a small label sticker, the RFID tag 100 can be arranged in an area that does not interfere with the display of the product on the label sticker of the plastic bottle.

In addition, the connection point between the first element 1 and the loop conductor 20 is not limited thereto, and may also be the peripheral portion of the loop conductor 20 in the negative direction of the X axis. With this structure, the first element 1 can be arranged in the area on the negative side of the loop conductor 20 in the X axis. Therefore, the width of the entire antenna portion 30 in the Y axis direction becomes narrower, and a slender RFID tag 100 can be realized. Therefore, even when the RFID tag 100 is attached to a large-capacity plastic bottle with a large height in the X axis direction, the RFID tag 100 can still be arranged in an area that does not hinder the display of the product in the plastic bottle.

The second element 2 is, for example, a linear conductive wiring pattern extending from the loop conductor 20 toward the negative direction of the X axis. The second element 2 is a linear element.

The end of the second element 2 in the positive direction of the X axis is connected to the first element 1 or the loop conductor 20.

When the second element 2 is connected to the first element 1, the second element 2 is connected, for example, near the connection between the first element 1 and the loop conductor 20. The second element 2 extends a certain distance from the connection toward the negative direction of the X axis.

When the second element 2 is connected to the loop conductor 20, the second element 2 is connected to, for example, the peripheral portion of the loop conductor 20 on the positive direction side of the Y axis.

The second element 2 can be disposed on the negative Y-axis direction side of the first element 1 , or can be disposed on the positive Y-axis direction side of the first element 1 .

As shown in FIG. 2 , when the second element 2 is disposed on the negative Y-axis side of the first element 1, the area on the negative X-axis side of the loop conductor 20 can be effectively utilized. Therefore, an RFID tag 100 having a smaller ratio of longitudinal width to transverse width can be realized.

In addition, if the gap between the second element 2 and the first element 1 (separation distance in the Y-axis direction) is set to a value of, for example, 0.5 mm to 2.0 mm, it is easy to obtain complex conjugation of the impedance of the antenna and the IC chip, which is preferred. If the distance becomes too large, the real part of the impedance becomes large, and it is difficult to obtain complex conjugation of the IC chip. The second element 2 is the main part, and the first element 1 is the auxiliary part.

The third element 3 is a hook-shaped conductive wiring pattern, which extends from the front end of the second element 2 in the negative direction of the X axis in a direction different from the extending direction of the second element 2. The third element 3 is a hook element. The third element 3 can be a U-shaped pattern or an L-shaped pattern.

In addition, the second element 2 and the third element 3 may also be integrally formed into a hook shape.

As shown in FIG. 2 , the third element 3 extends a certain distance in the negative direction of the Y axis from the front end of the second element 2 in the negative direction of the X axis, then bends vertically in the positive direction of the X axis and extends a certain distance toward the loop conductor 20. With this shape, the area on the negative direction side of the loop conductor 20 in the X axis can be effectively utilized. Therefore, an RFID tag 100 with a smaller ratio of longitudinal width to transverse width can be realized.

A gap is formed between the portion of the third element 3 extending toward the loop conductor 20 and the second element. This gap (separation distance in the Y-axis direction) is set to a value of, for example, 1.0 mm to 30.0 mm. A plurality of fourth elements 4 are disposed in this gap.

The fourth element 4 is a conductive wiring pattern, which extends from the second element 2 toward the third element 3, and forms a lattice-shaped pattern together with the second element 2 and the third element 3. The fourth element 4 is a lattice element.

In the present embodiment, three fourth elements 4 are used as an example, but the number of fourth elements 4 may be one or more. If the interval between adjacent fourth elements 4 in the X-axis direction is set to a value of, for example, 1.0 mm to 30.0 mm, the communicable frequency band is widened and the communication distance is extended, which is preferably

The electrical length of each component is set as follows.

For example, the length of the first element 1 is set to an electrical length that is a multiple of λ/4 of the wavelength of the use frequency. At this time, at least one of the length of the second element 2 and the length of the third element 3 is set to an electrical length different from the electrical length that is a multiple of λ/4. The different electrical length is, for example, in the range of λ/3.5 to λ/4.5 of the wavelength of the use frequency.

In addition, the electrical length of the second element 2 may be set to a multiple of λ/4 of the wavelength of the use frequency instead of the first element 1. In this case, at least one of the electrical length of the first element 1 and the electrical length of the third element 3 is set to an electrical length different from the electrical length of the multiple of λ/4 of the wavelength of the use frequency. The different electrical length in this case is, for example, in the range of λ/3.5 to λ/4.5 of the wavelength of the use frequency.

Furthermore, instead of the first element 1, the sum of the electrical length of the second element 2 and the electrical length of the L-shaped (inverted L-shaped) third element 3 may be set to a multiple of λ/4 of the wavelength of the use frequency. In this case, the electrical length of the first element 1 is set to an electrical length different from the electrical length of the multiple of λ/4 of the wavelength of the use frequency. The different electrical length in this case is, for example, in the range of λ/3.5 to λ/4.5 of the wavelength of the use frequency.

Furthermore, instead of the first element 1, the total electrical length of the electrical length of the second element 2, the electrical length of the third element 3, and the electrical length of the fourth element 4 (for example, any one of the three fourth elements 4) may be set to a multiple of λ/4 of the wavelength of the use frequency. In this case, the electrical length of the first element 1 is set to an electrical length different from the electrical length of the multiple of λ/4 of the wavelength of the use frequency. The different electrical length in this case is, for example, in the range of λ/3.5 to λ/4.5 of the wavelength of the use frequency.

Next, the impedance characteristics of the RFID tag 100 will be described using FIGS. 3A and 3B.

Fig. 3A is a diagram showing the impedance characteristics of the RFID tag 100 measured in a state where the liquid 200 is not contained in the container 300. Fig. 3B is a diagram showing the impedance characteristics of the RFID tag 100 measured in a state where the liquid 200 is contained in the container 300.

The impedance Zc of the RFID tag 100 is set to "Zc=Rc+jXc", and the vertical axis represents the values of real numbers and imaginary numbers. The subscript "c" is an abbreviation of the chip (IC chip 10). The horizontal axis represents the frequency of the radio wave for wireless communication. The solid line is a graph showing the real numbers corresponding to each frequency. The one-point link is a graph showing the imaginary numbers corresponding to each frequency.

In Figure 3A, the real value at 920 MHz is about 8 Ω, and the imaginary value at 920 MHz is about 176 Ω. In Figure 3B, the real value at 920 MHz is about 21 Ω, and the imaginary value at 920 MHz is about 198 Ω. This shows that the impedance characteristics change depending on whether there is liquid in the container.

The impedance characteristics shown in FIG. 3A and FIG. 3B are less turbulent than the impedance characteristics of the comparative example described later. Less turbulence in the impedance characteristics means less degradation in antenna performance. FIG. 4 is used to explain the comparative example of this embodiment.

Fig. 4 is a diagram showing a structural example of a comparative example 100A of the RFID tag 100 according to the embodiment of the present invention. The comparative example 100A includes an element 31 which is a zigzag wiring pattern, instead of the first element 1, the second element 2, and the third element 3.

The element 31 is a rectangular conductive wiring pattern, which is connected to the loop conductor 20 and extends from the loop conductor 20 in the X-axis direction. The element 31 is set to have an electrical length that is a multiple of approximately 1/4 of the wavelength of the use frequency. Approximately 1/4 includes, for example, approximately 1/3 to 1/5 of the wavelength of the use frequency.

The impedance characteristics of the comparative example 100A constructed in this way are described using FIGS. 5A and 5B.

FIG. 5A is a graph showing the impedance characteristics of the comparative example 100A measured in a state where the liquid 200 is not contained in the container 300. FIG. 5B is a graph showing the impedance characteristics of the comparative example 100A measured in a state where the liquid 200 is contained in the container 300. As in FIG. 3A and FIG. 3B, the vertical axis represents the values of real numbers and imaginary numbers. The horizontal axis represents the frequency of the radio wave for wireless communication. The solid line is a graph plotting the real numbers corresponding to each frequency. The dotted link is a graph plotting the imaginary numbers corresponding to each frequency.

In FIG. 5A , the value of the real number at 920 MHz is about 17 Ω, and the value of the imaginary number at 920 MHz is about 243 Ω. In FIG. 5B , the value of the real number at 920 MHz is about 80 Ω, and the value of the imaginary number at 920 MHz is about 25 Ω.

It can be seen that the impedance characteristics shown in FIG. 5A and FIG. 5B are more chaotic than the impedance characteristics shown in FIG. 3A and FIG. 3B. It is generally believed that the electrical coupling between the meandering shape of the element 31 and the liquid with a dielectric constant ε of "80" is the cause of the greater chaos in the impedance characteristics. For example, when the element 31 is arranged in front of the liquid from the reader, that is, when the reader, the element 31 and the liquid are arranged in this order, the dielectric constant of the liquid causes the impedance of the comparative example 100A to change significantly. That is, it is inferred that in the comparative example 100A, in order to ensure the electrical length required for the wireless communication of the antenna unit 30, a meandering antenna element is used. Therefore, from the observation of the reader, the electrical coupling between the liquid on the back side of the element 31 and the antenna element is enhanced, and the impedance characteristics are significantly disturbed. In order to solve this problem, the following measures have been taken in the past: by providing a spacer between the antenna element and the container, the distance from the antenna element to the liquid is increased to reduce the electrical coupling; and by inserting a metal sheet between the antenna element and the container to reduce the electrical coupling.

On the other hand, it is known that radio waves in the higher frequency UHF band are easily absorbed by liquid. For example, when there is liquid between the reader and the element 31, part of the radio waves transmitted from the reader are absorbed by the liquid in the container, and the remaining weak radio waves are received by the element 31. That is, the reception intensity of the radio waves in the element 31 is reduced. The element 31 uses this radio wave as a carrier wave to transmit a signal related to the identification information to the reader, so the weak radio waves generated from the comparative example 100A are absorbed by the liquid in the container, and the reception intensity of the radio waves in the reader is reduced.

It can be further understood that when there is a liquid between the reader and the element 31, the wavelength of the radio wave will be slightly shortened due to the wavelength shortening effect of the liquid when the radio wave passes through the liquid. After the wavelength of the radio wave is shortened, the resonance conditions of the antenna part 30 and the IC chip 10 deviate, and the coaxial matching conditions are not met, and the maximum power cannot be obtained.

In the comparative example 100A, a meander-shaped element 31 is used, and the electrical length of the element 31 is set to a multiple of λ/4 of the wavelength of the frequency used. Therefore, the inventors of the present application have found that the wireless communication of the reader becomes difficult due to the above-mentioned electrical coupling, wavelength shortening effect, absorption attenuation of radio waves, etc.

In contrast, the RFID tag 100 of this embodiment can relax the electrical coupling between the antenna element and the liquid by using an antenna element having a shape other than at least a meandering shape. In addition, the RFID tag 100 can relax the electrical coupling between the antenna element and the liquid by combining a plurality of antenna elements having different shapes.

Furthermore, according to the RFID tag 100 of this embodiment, by combining a plurality of elements with different electrical lengths, the deviation of the resonance condition is compensated, and a stable matching circuit can be obtained relative to the wavelength shortening effect of the liquid.

According to the RFID tag 100 of this embodiment, by combining a plurality of antenna elements of different shapes or a plurality of elements of different electrical lengths, the reception intensity of radio waves in the antenna unit 30 can be improved.

The RFID tag 100 of the present embodiment can be configured as follows: The same reference numerals are given to the same parts as those of the RFID tag 100, and their descriptions are omitted, and only the different parts are described.

FIG. 6 is a diagram showing a structural example of the RFID tag 100-1 of the first variation. The RFID tag 100-1 is configured such that the distance in the Y-axis direction from the first element 1 to the second element 2 becomes larger. In the RFID tag 100-1, if the gap between the first element 1 and the second element 2 is set to a value of, for example, 2.0 mm to 5.0 mm, it is easier to obtain complex co-ordination between the antenna and the IC chip, which is preferred. If the gap between the first element 1 and the second element 2 becomes greater than 5.0 mm, the resistance of the antenna becomes higher, and the communication distance may be reduced.

Fig. 7A is a diagram showing the impedance characteristics of the RFID tag 100-1 measured in a state where the container 300 does not contain the liquid 200. Fig. 7B is a diagram showing the impedance characteristics of the RFID tag 100-1 measured in a state where the container 300 contains the liquid 200.

In FIG. 7A, the real value of 920 MHz is about 10 Ω, and the imaginary value of 920 MHz is about 177 Ω. In FIG. 7B, the real value of 920 MHz is about 23 Ω, and the imaginary value of 920 MHz is about 196 Ω. According to FIG. 7A and FIG. 7B, it can be seen that the impedance characteristics of the RFID tag 100-1 are less chaotic than the impedance characteristics of the aforementioned comparative example 100A.

According to the RFID tag 100-1, the same effect as that of the RFID tag 100 can be obtained. In addition, according to the RFID tag 100-1, for example, when the upper and lower widths of the first element 1 having a zigzag shape are uneven due to manufacturing tolerance, the gap between the first element 1 and the second element 2 is enlarged, and the contact of the first element 1 with the second element 2 can be suppressed. Therefore, it is unnecessary to manage the manufacturing tolerance of the first element 1, etc. In addition, since the gap between the first element 1 and the second element 2 is enlarged, the manufacturing of each wiring pattern becomes easy. As a result, the yield of the RFID tag 100-1 is improved, and the manufacturing cost can be reduced.

Fig. 8 is a diagram showing a configuration example of an RFID tag 100-2 according to a second variation. The RFID tag 100-2 omits the first element 1 compared to the RFID tag 100. The electrical length of each element is set as follows.

For example, the length of the second element 2 is set to an electrical length that is a multiple of λ/4 of the wavelength of the use frequency. At this time, the length of the third element 3 is set to an electrical length different from the electrical length that is a multiple of λ/4. The different electrical length is, for example, in the range of λ/3.5 to λ/4.5 of the wavelength of the use frequency.

In addition, the electrical length of the third element 3 may be set to a multiple of λ/4 of the wavelength of the use frequency instead of the second element 2. In this case, the length of the second element 2 is set to an electrical length different from the electrical length of the multiple of λ/4. The different electrical length is, for example, in the range of λ/3.5 to λ/4.5 of the wavelength of the use frequency.

Furthermore, instead of the second element 2, the total electrical length of the electrical length of the third element 3 and the electrical length of the fourth element 4 (for example, any one of the three fourth elements 4) may be set to a multiple of λ/4 of the wavelength of the use frequency. In this case, the electrical length of the second element 2 is set to an electrical length different from the electrical length of the multiple of λ/4 of the wavelength of the use frequency. The different electrical length in this case is, for example, in the range of λ/3.5 to λ/4.5 of the wavelength of the use frequency.

Fig. 9A is a diagram showing the impedance characteristics of the RFID tag 100-2 measured in a state where the container 300 does not contain the liquid 200. Fig. 9B is a diagram showing the impedance characteristics of the RFID tag 100-2 measured in a state where the container 300 contains the liquid 200.

In FIG. 9A, the real value of 920 MHz is about 11 Ω, and the imaginary value of 920 MHz is about 185 Ω. In FIG. 9B, the real value of 920 MHz is about 16 Ω, and the imaginary value of 920 MHz is about 196 Ω. According to FIG. 9A and FIG. 9B, it can be seen that the impedance characteristics of the RFID tag 100-2 are less chaotic than the impedance characteristics of the aforementioned comparative example 100A.

According to the RFID tag 100-2, by combining a plurality of elements having different electrical lengths and shapes, the same effect as the RFID tag 100 can be obtained.

Furthermore, according to the RFID tag 100-2, for example, since the first element 1 is not required, not only is it unnecessary to manage the manufacturing tolerance of the first element 1, but the structure is also simplified. As a result, the yield of the RFID tag 100-2 is improved, and the manufacturing cost can be further reduced.

Fig. 10 is a diagram showing a configuration example of an RFID tag 100-3 according to a third variation. The number of fourth elements 4 in the RFID tag 100-3 is smaller than that in the RFID tag 100-2.

FIG. 11A is a diagram showing the impedance characteristics of the RFID tag 100-3 measured in a state where the container 300 does not contain the liquid 200. FIG. 11B is a diagram showing the impedance characteristics of the RFID tag 100-3 measured in a state where the container 300 contains the liquid 200.

In FIG. 11A, the value of the real number of 920 MHz is about 11 Ω, and the value of the imaginary number of 920 MHz is about 184 Ω. In FIG. 11B, the value of the real number of 920 MHz is about 17 Ω, and the value of the imaginary number of 920 MHz is about 196 Ω. According to FIG. 11A and FIG. 11B, it can be seen that the impedance characteristics of the RFID tag 100-3 are less chaotic than the impedance characteristics of the aforementioned comparative example 100A. In addition, according to FIG. 11A and FIG. 11B, it can be seen that the impedance characteristics of the RFID tag 100-3 are not significantly chaotic compared with the impedance characteristics of the RFID tag 100-2 of the aforementioned second variation.

According to the RFID tag 100-3, by combining a plurality of elements having different electrical lengths and shapes, the same effect as the RFID tag 100 can be obtained.

Furthermore, according to the RFID tag 100-3, for example, the number of the fourth element 4 can be reduced, and accordingly, the management of manufacturing tolerance is not required, and the structure is also simplified. As a result, the yield of the RFID tag 100-3 is improved, and the manufacturing cost can be further reduced.

Fig. 12 is a diagram showing a structural example of an RFID tag 100-4 according to a fourth variation. Compared to the RFID tag 100-3, the RFID tag 100-4 uses a fifth element 5 instead of the third element 3 and the fourth element 4. The second element 2 is a main part, and the fifth element 5 is a secondary part.

The fifth element 5 is a conductor that is connected to the second element 2 in a manner of branching from the middle of the second element 2, which is a linear element, and extends in parallel with the second element 2. The fifth element 5 is a branch element.

The connection point of the fifth element 5 to the second element 2 is, for example, a position separated by a specific distance from the connection point of the second element 2 and the loop conductor 20. If the specific distance is set to a value of, for example, 5.0 mm to 100.0 mm, the resistance of the antenna will not be too high, which is preferred.

A gap is formed between the second element 2 and the fifth element 5 extending in opposite directions along the side of the loop conductor 20. If this gap (separation distance in the Y-axis direction) is set to a value of, for example, 1.0 mm to 30.0 mm, the resistance of the antenna will not be too high, which is preferred. In addition, the fourth element 4 mentioned above can also be set in this gap.

The electrical length of each component is set as follows.

For example, the length of the second element 2 is set to an electrical length that is a multiple of λ/4 of the wavelength of the use frequency. At this time, the length of the fifth element 5 is set to an electrical length different from the electrical length that is a multiple of λ/4. The different electrical length is, for example, in the range of λ/3.5 to λ/4.5 of the wavelength of the use frequency.

Furthermore, the electrical length of the fifth element 5 may be set to a multiple of λ/4 of the wavelength of the use frequency instead of the second element 2. In this case, the electrical length of the second element 2 is set to an electrical length different from the electrical length of the multiple of λ/4 of the wavelength of the use frequency. The different electrical length in this case is, for example, in the range of λ/3.5 to λ/4.5 of the wavelength of the use frequency.

Fig. 13A is a diagram showing the impedance characteristics of the RFID tag 100-4 measured in a state where the liquid 200 is not contained in the container 300. Fig. 13B is a diagram showing the impedance characteristics of the RFID tag 100-4 measured in a state where the liquid 200 is contained in the container 300.

In FIG. 13A, the value of the real number of 920 MHz is about 9 Ω, and the value of the imaginary number of 920 MHz is about 184 Ω. In FIG. 13B, the value of the real number of 920 MHz is about 16 Ω, and the value of the imaginary number of 920 MHz is about 193 Ω. According to FIG. 13A and FIG. 13B, it can be seen that the impedance characteristics of the RFID tag 100-4 are less chaotic than the impedance characteristics of the aforementioned comparative example 100A. In addition, according to FIG. 13A and FIG. 13B, it can be seen that the impedance characteristics of the RFID tag 100-4 are roughly the same as the impedance characteristics of the RFID tag 100-3 of the aforementioned third variation, and are not significantly chaotic.

According to the RFID tag 100-4, by combining a plurality of elements having different electrical lengths and shapes, the same effect as the RFID tag 100 can be obtained.

Furthermore, according to the RFID tag 100-4, the fourth element 4 can be omitted, and accordingly, the management of manufacturing tolerance is not required, and the structure is simplified. As a result, the yield of the RFID tag 100-4 is improved, and the manufacturing cost can be further reduced.

Furthermore, according to the RFID tag 100-4, since the branch position of the fifth element 5 is easily adjusted, that is, the position of the fifth element 5 pulled out from the second element 2 is easily adjusted, the design conditions of the RFID tag 100-4 can be made free. For example, when the surface area of the RFID tag 100-4 must be minimized as much as possible, the area on the lower side (negative Y-axis side) of the second element 2 is expected to be narrowed. At this time, after the branch position of the fifth element 5 is maximized to be close to the loop conductor 20, by shortening the length of the portion extending along the X-axis direction of the fifth element 5, it can also be applied to the special container 300. Therefore, the number of containers 300 to which the RFID tag 100 - 4 can be applied increases, and the production volume of the RFID tag 100 - 4 can be increased accordingly, which can further reduce the manufacturing unit price of the RFID tag 100 - 4.

FIG. 14 is a diagram showing a structural example of an RFID tag 100-5 according to a fifth variation. Compared to the RFID tag 100-4, the fifth element 5 is omitted in the RFID tag 100-5. The RFID tag 100-5 has a simple structure having a second element 2 instead of a structure in which a plurality of elements having different electrical lengths and shapes are combined.

The second element 2 of the RFID tag 100-5 is a straight-line conductor whose electrical length is set to be a multiple of approximately λ/4 of the wavelength of the frequency used.

The inventor of the present application has confirmed that the impedance characteristics of the RFID tag 100-5 are equivalent to the impedance characteristics shown in, for example, FIG. 13A and FIG. 13B. The inventor of the present application has also confirmed that the impedance characteristics of the RFID tag 100-5 are less chaotic than the impedance characteristics of the aforementioned comparative example 100A.

In addition, it is confirmed that the communication distance between the RFID tag 100-5 and the reader may be shorter than the communication distance between the RFID tags 100 to 100-4, but at least a practical communication distance (e.g., about 1 m to 7 m) can be ensured. In addition, even if the communication distance is shortened, by configuring a reader on a belt conveyor for transporting containers, identification information can be read, so it can be flexibly used for inventory management of all products.

The reason why the impedance characteristics are excellent is considered to be that the antenna element is made into a straight line shape, thereby weakening the electrical coupling between the antenna element and the liquid compared to the case of using only a meandering antenna element.

In the past, in order to ensure the electrical length required for wireless communication of the antenna unit 30, a meander-shaped antenna element, a ring-shaped antenna element, etc., was often used. However, if such an antenna element is used, the electrical coupling with the liquid is enhanced, and the impedance characteristics are significantly disturbed, so that the desired antenna performance cannot be ensured. Therefore, the following measures have been taken in the past: by providing a spacer between the antenna element and the container, the distance from the antenna element to the liquid is increased to reduce the electrical coupling; and by inserting a metal sheet between the antenna element and the container to reduce the electrical coupling, etc.

According to the RFID tag 100-5 of the fifth variation, such measures are not required, so the management of the manufacturing of the RFID tag 100-5 becomes easy, and the materials required for manufacturing the RFID tag 100-5 can be greatly reduced. Therefore, it is possible to achieve a significant reduction in the manufacturing cost of the RFID tag 100-5.

Fig. 15 is a diagram showing a structural example of an RFID tag 100-6 according to a sixth variation. In the RFID tag 100-6, the fourth element 4 is omitted compared to the RFID tag 100-3 according to the third variation.

The inventors of this application have confirmed that the impedance characteristics of the RFID tag 100-6 are less chaotic than the impedance characteristics of the aforementioned comparative example 100A. In addition, it has been confirmed that the communication distance between the RFID tag 100-6 and the reader is equivalent to the communication distance between the RFID tag 100-3 and the reader.

According to the RFID tag 100-6, for example, the fourth element 4 can be omitted, and accordingly, the management of manufacturing tolerance is not required, and the structure is simplified. As a result, the yield of the RFID tag 100-6 is improved, and the manufacturing cost can be further reduced.

Fig. 16 is a diagram showing a structural example of the RFID tag 100-7 of the seventh variation. Compared with the RFID tag 100, the third element 3 and the fourth element 4 are omitted in the RFID tag 100-7. When the first element 1 is the main part, the second element 2 becomes the auxiliary part; and when the second element 2 is the main part, the first element 1 becomes the auxiliary part.

The electrical length of each component is set as follows.

For example, the length of the first element 1 is set to an electrical length that is a multiple of λ/4 of the wavelength of the use frequency. At this time, the length of the second element 2 is set to an electrical length different from the electrical length that is a multiple of λ/4. The different electrical length is, for example, in the range of λ/3.5 to λ/4.5 of the wavelength of the use frequency.

In addition, the electrical length of the second element 2 may be set to a multiple of λ/4 of the wavelength of the use frequency instead of the first element 1. In this case, the electrical length of the first element 1 is set to an electrical length different from the electrical length of the multiple of λ/4 of the wavelength of the use frequency. The different electrical length in this case is, for example, in the range of λ/3.5 to λ/4.5 of the wavelength of the use frequency.

The inventors of the present application have confirmed that the impedance characteristics of the RFID tag 100-7 are less chaotic than the impedance characteristics of the aforementioned comparative example 100A. In addition, the communication distance between the RFID tag 100-7 and the reader is equivalent to the communication distance between the RFID tag 100 and the reader.

According to the RFID tag 100-7, for example, the third element 3 and the fourth element 4 can be omitted, and accordingly, the management of manufacturing tolerance is not required, and the structure is simplified. As a result, the yield of the RFID tag 100-7 is improved, and the manufacturing cost can be further reduced.

Fig. 17 is a diagram showing a structural example of an RFID tag 100-8 according to the eighth variation. Compared with the RFID tag 100, the RFID tag 100-8 uses a fifth element 5 instead of the third element 3 and the fourth element 4. When the first element 1 is the main part, the second element 2 becomes the auxiliary part; and when the second element 2 is the main part, the first element 1 becomes the auxiliary part.

The electrical length of each component is set as follows.

For example, when the length of the first element 1 is set to an electrical length that is a multiple of λ/4 of the wavelength of the use frequency, at least one of the length of the second element 2 and the length of the fifth element 5 is set to an electrical length different from the electrical length that is a multiple of λ/4. The different electrical lengths are, for example, in the range of λ/3.5 to λ/4.5 of the wavelength of the use frequency.

Furthermore, when the length of the second element 2 is set to an electrical length that is a multiple of λ/4 of the wavelength of the use frequency, at least one of the length of the first element 1 and the length of the fifth element 5 is set to an electrical length different from the electrical length that is a multiple of λ/4. The different electrical lengths are, for example, in the range of λ/3.5 to λ/4.5 of the wavelength of the use frequency.

Furthermore, when the electrical length of the fifth element 5 is set to a multiple of λ/4 of the wavelength of the use frequency, at least one of the electrical length of the first element 1 and the length of the second element 2 is set to an electrical length different from the electrical length of the multiple of λ/4. The different electrical length is, for example, in the range of λ/3.5 to λ/4.5 of the wavelength of the use frequency.

The inventors of this application have confirmed that the impedance characteristics of the RFID tag 100-8 are less chaotic than the impedance characteristics of the aforementioned comparative example 100A. In addition, it has also been confirmed that the communication distance between the RFID tag 100-8 and the reader is equivalent to the communication distance between the RFID tag 100 and the reader.

According to the RFID tag 100-8, for example, the fourth element 4 can be omitted, and accordingly, the management of manufacturing tolerance is not required, and the structure is simplified. As a result, the yield of the RFID tag 100-8 is improved, and the manufacturing cost can be further reduced.

In addition, each of the RFID tags 100 to 100-8 of the present embodiment can be applied not only to radio waves in the UHF band, but also to radio waves in the VHF band, SHF band, etc. When the operating frequency of the RFID tags 100 to 100-8 is the frequency of the UHF band, such as 860 to 960 MHz, 915 to 925 MHz, etc., the UHF band is higher than the VHF band, so the wavelength becomes shorter, which is conducive to the miniaturization of the antenna. Therefore, by making the RFID tags 100 to 100-8 of the present embodiment into a shape suitable for radio waves in the UHF band, the miniaturization of the IC chip 10 can be achieved, and a wireless tag with small memory capacity and low price can be obtained.

Furthermore, each of the RFID tags 100 to 100-8 of the present embodiment can be applied to any of electromagnetic induction type wireless tags and radio wave type wireless tags. In particular, when the RFID tags 100 to 100-8 are applied to radio wave type wireless tags, a specific wireless communication distance with a reader can be ensured. The specific wireless communication distance is, for example, in the range of 0 m to 20 m.

In addition, the RFID tags 100 to 100-8 of this embodiment can still achieve wireless communication using radio waves such as UHF band, VHF band, SHF band, etc. when the surroundings of the RFID tags 100 to 100-8 are in either the air (in the atmosphere) or in water. For example, when the container 300 having the RFID tags 100 to 100-8 is contained in a bucket, etc., the RFID tags 100 to 100-8 can be used to achieve wireless communication with the reader regardless of whether the bucket is in a state where no water is added or in a state where water is added. The following describes how the RFID tag 100-9 of the ninth variation having the same technical features as the RFID tags 100 to 100-8 can achieve wireless communication even when placed in either the air or in water.

FIG. 18A is a first diagram showing the frequency characteristics of an RFID tag placed in the air. FIG. 18B is a second diagram showing the frequency characteristics of an RFID tag placed in the air. FIG. 18C is a third diagram showing the frequency characteristics of an RFID tag placed in the air. FIG. 18D is a fourth diagram showing the frequency characteristics of an RFID tag placed in the air. FIG. 18E is a fifth diagram showing the frequency characteristics of an RFID tag placed in the air.

FIG. 18A to FIG. 18E show the frequency characteristics of the RFID tag 100-9 placed in the air. The horizontal axis of each figure represents the frequency of the radio wave for wireless communication, and the vertical axis represents the communicable distance from the RFID tag 100-9 to the reader. In addition, the details of the structure of the RFID tag 100-9 are as follows.

FIG18A shows data of the RFID tag 100-9 placed on a 500 ml PET bottle (not frozen) containing liquid. As can be seen from FIG18A, in the case of a 500 ml PET bottle, the resonance frequency band that allows the communication distance to be 10 cm or more can be extended to 830 MHz to 1040 MHz.

FIG. 18B shows data of the RFID tag 100-9 placed on a 900 ml glass bottle containing alcohol (e.g., 25% ethanol added to water). As can be seen from FIG. 18B, in the case of a 900 ml glass bottle, a resonant frequency band of, for example, 740 MHz to 1200 MHz can be secured when the communication distance is 10 cm or more.

FIG18C shows data of the RFID tag 100-9 placed on a 1500 ml paper box containing water. As can be seen from FIG18C, in the case of a 1000 ml paper box, a resonance frequency band of, for example, 780 MHz to 1200 MHz can be secured when the communication distance is 10 cm or more.

FIG. 18D shows data of the RFID tag 100-9 placed on a 1000 ml PET bottle containing oil (Nissin Oillio salad oil). As can be seen from FIG. 18D, in the case of a 1000 ml PET bottle, a resonant frequency band of, for example, 700 MHz to 1200 MHz can be secured when the communication distance is 10 cm or more.

FIG. 18E shows data of the RFID tag 100-9 placed on a 500 ml PET bottle (frozen) containing liquid. As can be seen from FIG. 18E, in the case of a frozen PET bottle, a resonance frequency band of, for example, 700 MHz to 1200 MHz can be secured when the communication distance is 10 cm or more.

Next, referring to FIGS. 19A to 20D, the frequency characteristics before and after a 500 ml plastic bottle equipped with an RFID tag 100-9 is placed in a bucket and water is added to the bucket are described.

FIG. 19A is a first diagram for explaining the frequency characteristics of an RFID tag that can be set in either the air or the water. FIG. 19B is a second diagram for explaining the frequency characteristics of an RFID tag that can be set in either the air or the water. FIG. 19C is a third diagram for explaining the frequency characteristics of an RFID tag that can be set in either the air or the water. FIG. 19D is a fourth diagram for explaining the frequency characteristics of an RFID tag that can be set in either the air or the water.

As shown in FIGS. 19A to 19D, a 500 ml plastic bottle (container 300) is contained in a bucket (container 400) that can contain water 311. FIG. 19A shows a state where water 311 has not been added to the container 400, and FIGS. 19B to 19C show a state where water 311 has been added to the container 400.

The amount of water 311 is increased in the order of FIG. 19B, FIG. 19C, and FIG. 19D. The state of FIG. 19B is before the RFID tag 100-9 is immersed in water, that is, most of the container 300 is immersed in water 311 but the RFID tag 100-9 has not yet been immersed in water 311. The state of FIG. 19C is the state of the RFID tag 100-9 just after being immersed in water, that is, only a small amount of water 311 exists on the top of the RFID tag 100-9. The state of a small amount of water 311 means, for example, that the distance from the surface of the RFID tag 100-9 to the water surface 311a is about 1 mm to 1 cm. The state of FIG. 19D is that compared with the state of FIG. 19C, the amount of water 311 is increased, for example, the distance from the RFID tag 100-9 to the water surface 311a is about 10 cm.

The frequency characteristics of the RFID tag 100-9 verified under these conditions are shown in FIGS. 20A to 20D. FIG. 20A is a diagram showing the frequency characteristics of the RFID tag shown in FIG. 19A, FIG. 20B is a diagram showing the frequency characteristics of the RFID tag shown in FIG. 19B, FIG. 20C is a diagram showing the frequency characteristics of the RFID tag shown in FIG. 19C, and FIG. 20D is a diagram showing the frequency characteristics of the RFID tag shown in FIG. 19D. The horizontal axis of each figure represents the frequency of the radio wave for wireless communication, and the vertical axis represents the communicable distance from the RFID tag 100-9 to the reader. In addition, as shown in FIG. 19A , these data are measured when the distance L between the antenna 500 for the reader and the RFID tag 100 - 9 is 25 cm.

The frequency characteristics of FIG. 20A correspond to the state of FIG. 19A. As can be seen from FIG. 20A, when no water 311 is added to the container 400, the resonance frequency band can be ensured to be expanded to 800 MHz to 1200 MHz when the communication distance is 10 cm or more.

The frequency characteristics of Fig. 20B correspond to the state of Fig. 19B. As can be seen from Fig. 20B, the resonance frequency band when the communication distance is 10 cm or more when the RFID tag 100-9 is not immersed in water 311 can be ensured to be expanded to 800 MHz to 1200 MHz.

The frequency characteristics of FIG. 20C correspond to the state of FIG. 19C. As can be seen from FIG. 20C, when the RFID tag 100-9 is slightly immersed in water 311, the overall communication distance becomes shorter compared to the data of FIG. 20B, but the communication distance can be extended except for the vicinity of 840 MHz and 1100 MHz.

The frequency characteristics of FIG. 20D correspond to the state of FIG. 19D. As can be seen from FIG. 20D, when the distance from the RFID tag 100-9 to the water surface 311a becomes longer, the communication distance can still be extended.

In addition, although no example data is shown in the present embodiment, it has been demonstrated that when the distance from the RFID tag 100-9 to the water surface 311a is longer than 15 cm, for example, if the distance is about 30 cm, wireless communication using the RFID tag 100-9 can be achieved.

Fig. 21 is a diagram showing a configuration example of an RFID tag 100-9 according to a ninth variation. The difference from the RFID tag 100-2 shown in Fig. 8 is that the number of fourth elements 4 in the RFID tag 100-9 is increased.

According to the RFID tag 100-9, the electrical coupling between the antenna element and the liquid can be alleviated. Furthermore, according to the RFID tag 100-9, by combining a plurality of elements with different electrical lengths, the deviation of the resonance condition is compensated, and a stable matching circuit can be obtained relative to the wavelength shortening effect of the liquid. Furthermore, according to the RFID tag 100-9, by combining a plurality of elements with different electrical lengths, the reception intensity of the radio waves in the antenna part 30 can be improved. In particular, by increasing the number of the fourth element 4, the reception intensity of the radio waves in the antenna part 30 can be further improved even when used in water. Furthermore, according to the RFID tag 100-9, the use in the air is taken as the basis, and for example, in the case of opening a store, in order to cool the plastic bottle, even if the plastic bottle is immersed in a container filled with ice water, etc., inventory management can still be achieved. Therefore, the labor of taking out the plastic bottles from the container filled with ice water and checking the inventory number can be saved. In addition, even if the plastic bottles are soaked in water due to earthquakes, floods, etc., the inventory number can still be checked under the condition of being soaked in water.

The structures shown in the above embodiments are examples of the contents of the present invention, and other known technologies may be combined, and part of the structures may be omitted or changed as long as they do not deviate from the gist of the present invention.

This international application claims priority based on Japanese Patent Application No. 2019-134033 filed on July 19, 2019 and Japanese Patent Application No. 2019-195734 filed on October 28, 2019, and the entire contents of No. 2019-134033 and No. 2019-195734 are hereby incorporated by reference into this international application.

1: First element 2: Second element 3: Third element 4: Fourth element 5: Fifth element 10: IC chip 20: Loop conductor 30: Antenna part 30A, 30B: Conductor part 31: Element 40: Sheet 100, 100-1, 100-2, 100-3, 100-4, 100-5, 100-6, 100-7, 100-8, 100-9: RFID tag 200: Liquid 300: Container 301: Cover 302: Label sticker

FIG. 1 is a perspective view of a liquid container 300 in which an RFID tag of an embodiment of the present invention is provided. FIG. 2 is a diagram showing a structural example of an RFID tag. FIG. 3A is a diagram showing the impedance characteristics of an RFID tag measured in a state where no liquid is contained in the container. FIG. 3B is a diagram showing the impedance characteristics of an RFID tag measured in a state where liquid is contained in the container. FIG. 4 is a diagram showing a structural example of a comparative example of an RFID tag of an embodiment of the present invention. FIG. 5A is a diagram showing the impedance characteristics of a comparative example measured in a state where no liquid is contained in the container. FIG. 5B is a diagram showing the impedance characteristics of a comparative example measured in a state where liquid is contained in the container. FIG. 6 is a diagram showing a structural example of an RFID tag of a first variation. FIG. 7A is a diagram showing the impedance characteristics of the RFID tag measured when no liquid is contained in the container. FIG. 7B is a diagram showing the impedance characteristics of the RFID tag measured when the liquid is contained in the container. FIG. 8 is a diagram showing a structural example of the RFID tag of the second variation. FIG. 9A is a diagram showing the impedance characteristics of the RFID tag measured when no liquid is contained in the container. FIG. 9B is a diagram showing the impedance characteristics of the RFID tag measured when the liquid is contained in the container. FIG. 10 is a diagram showing a structural example of the RFID tag of the third variation. FIG. 11A is a diagram showing the impedance characteristics of the RFID tag measured when no liquid is contained in the container. FIG. 11B is a diagram showing the impedance characteristics of the RFID tag measured when the liquid is contained in the container. FIG. 12 is a diagram showing a structural example of an RFID tag of the fourth variation. FIG. 13A is a diagram showing the impedance characteristics of the RFID tag measured in a state where no liquid is contained in the container. FIG. 13B is a diagram showing the impedance characteristics of the RFID tag measured in a state where a liquid is contained in the container. FIG. 14 is a diagram showing a structural example of an RFID tag of the fifth variation. FIG. 15 is a diagram showing a structural example of an RFID tag of the sixth variation. FIG. 16 is a diagram showing a structural example of an RFID tag of the seventh variation. FIG. 17 is a diagram showing a structural example of an RFID tag of the eighth variation. FIG. 18A is a first diagram showing the frequency characteristics of an RFID tag set in the air. FIG. 18B is a second diagram showing the frequency characteristics of an RFID tag set in the air. FIG. 18C is a third diagram showing the frequency characteristics of an RFID tag set in the air. FIG. 18D is a fourth diagram showing the frequency characteristics of an RFID tag set in the air. FIG. 18E is a fifth diagram showing the frequency characteristics of an RFID tag set in the air. FIG. 19A is a first diagram showing the frequency characteristics of an RFID tag that can be set in either the air or the water. FIG. 19B is a second diagram showing the frequency characteristics of an RFID tag that can be set in either the air or the water. FIG. 19C is a third diagram showing the frequency characteristics of an RFID tag that can be set in either the air or the water. FIG. 19D is a fourth diagram showing the frequency characteristics of an RFID tag that can be set in either the air or the water. FIG. 20A is a diagram showing the frequency characteristics of the RFID tag shown in FIG. 19A. FIG. 20B is a diagram showing the frequency characteristics of the RFID tag shown in FIG. 19B. FIG. 20C is a diagram showing the frequency characteristics of the RFID tag shown in FIG. 19C. FIG. 20D is a diagram showing the frequency characteristics of the RFID tag shown in FIG. 19D. FIG. 21 is a diagram showing a structural example of an RFID tag of the ninth variation.

Domestic storage information (please note in the order of storage institution, date, and number) None Foreign storage information (please note in the order of storage country, institution, date, and number) None

1: First element

2: Second element

3: The third element

4: The fourth element

10: IC chip

20: Loop conductor

30: Antenna Department

30A, 30B: Conductor part

40: Sheet

Claims (18)

An RFID tag is provided on the surface of a container for containing liquid, and comprises: an IC chip recording identification information; a loop conductor connected to the IC chip; and an antenna portion having two linear elements, the linear elements being linear conductors connected to the loop conductor and extending from the loop conductor in directions separated from each other, and having an electrical length set to be a multiple of approximately λ/4 of the wavelength of a frequency of use; one of the two linear elements extends in one direction away from the loop conductor, and the other of the two linear elements extends in a direction opposite to the one direction away from the loop conductor. An RFID tag is provided on the surface of a container containing liquid, and the RFID tag comprises: an IC chip recording identification information; a loop conductor connected to the IC chip; and an antenna portion having two main portions and two secondary portions, wherein the two main portions are conductors connected to the loop conductor and extending from the loop conductor in directions separating from each other, and the two secondary portions are conductors branching from the main portion and connected to the front antenna. The main part is connected to the main part and extends in parallel with the main part; one of the two main parts extends in a direction away from the loop conductor, and the other of the two main parts extends in a direction opposite to the direction away from the loop conductor; and one of the main part and the auxiliary part is set to an electrical length that is a multiple of approximately λ/4 of the wavelength of the use frequency, and the other is set to an electrical length different from the electrical length. An RFID tag is disposed on the surface of a container containing liquid, and comprises: an IC chip recording identification information; a loop conductor connected to the IC chip; and an antenna portion having two main portions and two secondary portions, wherein the two main portions are conductors connected to the loop conductor and extending from the loop conductor in directions separating from each other, and the two secondary portions are zigzag antennas connected to the loop conductor. shaped conductor; one of the two main parts extends in one direction away from the loop conductor, and the other of the two main parts extends in a direction opposite to the one direction away from the loop conductor; and one of the main part and the auxiliary part is set to an electrical length that is a multiple of approximately λ/4 of the wavelength of the use frequency, and the other is set to an electrical length different from the electrical length. An RFID tag is provided on the surface of a container for containing liquid, and comprises: an IC chip recording identification information; a loop conductor connected to the IC chip; and an antenna portion, which is two lattice-shaped conductors connected to the loop conductor and extending from the loop conductor in directions separating from each other, and having an electrical length set to be a multiple of approximately λ/4 of the wavelength of a frequency of use; one of the two conductors extends in a direction away from the loop conductor, and the other of the two conductors extends in a direction opposite to the direction away from the loop conductor. The RFID tag as described in claim 1, wherein the antenna portion has a branch element, the branch element is a conductor, which is connected to the linear element in a manner of branching from the middle of the linear element and extends parallel to the linear element; and the length of the branch element is set to an electrical length different from the electrical length. The RFID tag as described in claim 1, wherein the antenna portion has a hook element, which is a hook-shaped conductor, which is disposed at the front end of the linear element and extends from the front end of the linear element in a direction different from the direction in which the linear element extends; and the length of the hook element is set to an electrical length different from the electrical length. The RFID tag as described in claim 5, wherein the antenna portion has a lattice element, which is a conductor extending from the linear element toward the branch element, and the linear element and the branch element together form a lattice-shaped pattern. The RFID tag as described in claim 6, wherein the antenna portion has a lattice element, which is a conductor extending from the straight line element toward the hook element, and the straight line element and the hook element together form a lattice-shaped pattern. The RFID tag as described in any one of claims 1 to 8 uses a frequency in the UHF band, i.e., 860 to 960 MHz. The RFID tag as described in any one of claim items 1 to 8 is a radio wave wireless tag. An RFID tag as described in any one of claims 1 to 8, which is placed in the air. The RFID tag as described in any one of claims 1 to 8 can be placed in either the air or water. An RFID tag as described in any one of claim items 1 to 8, which is placed in water. The RFID tag as described in any one of claims 1 to 8 uses a frequency in the UHF band, i.e., 915 to 925 MHz. An RFID tag as described in any one of claims 1 to 8, wherein the liquid is any one of water, oil and alcohol. An RFID tag as described in any one of claims 1 to 8, wherein the aforementioned liquid is any mixture of water, oil and alcohol. A plastic bottle having an RFID tag as described in any one of claims 1 to 16 attached thereto. An antenna for use in an RFID tag as described in any one of claims 1 to 16.

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