RF tag antenna

Abstract

Provided are an antenna for RF tags that operates in a wide frequency band, and an RF tag.　An antenna 1 for RF tags according to the present invention comprises an insulating substrate 10, a main waveguide element 20, a base plate 30 that is electrically connected to the main waveguide element, an auxiliary waveguide element 40 that is connected to the main waveguide element via an IC chip 60, and a capacitor 203 for frequency adjustment. At least part of the auxiliary waveguide element overlaps the base plate with a coating layer 70 composed of an insulating material interposed therebetween, whereby a capacitor is formed by the auxiliary waveguide element, the coating layer, and the base plate. The insulating substrate is enclosed in ring form by the main waveguide element, the base plate, and the auxiliary waveguide element. The capacitor for frequency adjustment is provided between the main waveguide element and the auxiliary waveguide element. Due to the insulating substrate being enclosed in ring form, inductance increases, a resistance value increases, and the Q value of a series resonance circuit decreases. As a result, a bandwidth increases, making it possible to obtain an antenna for RF tags that operates in a wide frequency band and an RF tag.

Description

[Technical Field]

[0001] The present invention relates to an antenna for an RF tag that operates over a wide frequency band. [Background technology]

[0002] The RF tags used in RFID (Radio Frequency Identification) systems contain an antenna and an RF chip (IC chip), which receives the carrier wave transmitted from the antenna of the reader / writer and transmits the identification data recorded on the RF chip on a reflected wave back to the reader / writer, thereby achieving contactless communication.

[0003] RF tags may be required to operate over a wide frequency band. For example, the dual RF tag of Patent Document 1 has a low-band radiating element section, a high-band radiating element section, an inductor pattern section, a balance coil section, and an IC chip on the front surface, a ground element section on the back surface, and an insulating substrate between the front and back surfaces, which electrically connects the ground element section and the balance coil section. The low-band radiation element is connected to one end of the primary coil of the balance coil unit, the high-band radiation element to the other end, and a ground element is connected to the midpoint of the primary coil. Because the ground element is connected to the midpoint of the primary coil, a two-coil configuration is achieved, with the first coil extending from one end of the primary coil to the midpoint and the second coil extending from the other end of the primary coil to the midpoint. The low-band radiation element functions as an antenna for low frequencies, and the high-band radiation element functions as an antenna for high frequencies, allowing operation in two frequency bands without the need to switch between low and high bands using a switch mechanism.

[0004] Furthermore, the dual RF tag of Patent Document 2 comprises an insulating substrate, a main waveguide element, a secondary waveguide element, a ground plane, a power feed section, and a short-circuit section to form a planar inverted-F antenna. By changing the position of the secondary waveguide element and changing the area of ​​the portion where the secondary waveguide element and the main waveguide element face each other, the wavelength λ of the radio wave can be switched between low and high frequencies. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2019 / 039447 [Patent Document 2] International Publication No. 2022 / 118595 Summary of the Invention [Problem to be solved by the invention]

[0006] The technology of Patent Document 1 has a two-coil configuration, a first coil and a second coil, as the primary coil, but compared to a case where the primary coil is configured as a single coil from one end to the other, the transmission and reception power between the balance coil and the secondary coil is halved in the configuration of Patent Document 1. In this way, when operating in two frequency bands without a switch mechanism for switching between the low band and the high band, the transmission and reception power is reduced to halve, resulting in a problem of a shorter communication distance. The technique of Patent Document 2 requires changing the position of the sub-wavedirection element to switch between the low frequency side and the high frequency side, which causes problems such as the time-consuming changeover work and the increased manufacturing costs.

[0007] In consideration of such problems, the present invention has an object to provide an antenna for an RF tag that operates over a wide frequency band. [Means for solving the problem]

[0008] The RF tag antenna of the present invention comprises an insulating substrate, a main waveguide element, a ground plate electrically connected to the main waveguide element, a secondary waveguide element connected to the main waveguide element via an IC chip, and a frequency adjustment capacitor, wherein the main waveguide element is provided on the front surface of the insulating substrate and the ground plate is provided on the back surface of the insulating substrate, and at least a portion of the secondary waveguide element overlaps with the ground plate via a coating layer made of an insulating material, thereby forming a capacitor with the secondary waveguide element, the coating layer and the ground plate, and the main waveguide element, the ground plate and the secondary waveguide element surround the insulating substrate in a ring shape, and the frequency adjustment capacitor is provided between the main waveguide element and the secondary waveguide element. The frequency adjustment capacitor is composed of a first extension piece extending from an end of the main waveguide element to the sub-direction element side, a second extension piece facing the first extension piece and extending from the end of the sub-direction element to the main waveguide element side, and a gap formed between the tip of the first extension piece and the tip of the second extension piece. It is characterized by:

[0009] The device also includes an insulating substrate, a main waveguide element, a ground plane electrically connected to the main waveguide element, a secondary waveguide element connected to the main waveguide element via an IC chip, and a frequency adjustment capacitor, wherein the main waveguide element is provided on the front surface of the insulating substrate and the ground plane is provided on the back surface of the insulating substrate, and at least a portion of the secondary waveguide element overlaps with the ground plane via a coating layer made of an insulating material, thereby forming a capacitor with the secondary waveguide element, the coating layer, and the ground plane, and the main waveguide element, the ground plane, and the secondary waveguide element surround the insulating substrate in a ring shape, and the frequency adjustment capacitor is provided between the main waveguide element and the secondary waveguide element. The frequency adjustment capacitor is composed of an island piece disposed between the main waveguide element and the sub-directive element in an island shape, and gaps formed between the island piece and the main waveguide element and between the island piece and the sub-directive element. It is characterized by:

[0010] The RF tag antenna of the present invention comprises an insulating substrate, a primary waveguide element, a ground plate electrically connected to the primary waveguide element, a secondary waveguide element connected to the ground plate via an IC chip, and a frequency adjustment capacitor, wherein the primary waveguide element is provided on the surface of the insulating substrate and the ground plate is provided on the back surface of the insulating substrate, at least a portion of the secondary waveguide element overlaps with the primary waveguide element via a coating layer made of an insulating material, thereby forming a capacitor with the secondary waveguide element, the coating layer and the primary waveguide element, and the primary waveguide element, the ground plate and the secondary waveguide element surround the insulating substrate in a ring shape, and the frequency adjustment capacitor is provided between the ground plate and the secondary waveguide element.

[0011] Also, The frequency adjustment capacitor is composed of a frequency adjustment element made up of an insulating layer and a conductive layer, the insulating layer is laid between the ground plane and the sub-waveguide element, and the conductive layer is disposed on the insulating layer. It is characterized by: Also, The frequency adjustment capacitor is composed of a first extension piece extending from an end of the ground plane toward the auxiliary waveguide element, a second extension piece facing the first extension piece and extending from an end of the auxiliary waveguide element toward the main waveguide element, and a gap formed between the tip of the first extension piece and the tip of the second extension piece. It is characterized by:

[0012] Also, The frequency adjustment capacitor is composed of an island piece disposed in an island shape between the ground plane and the sub-wave director element, and a gap formed between the island piece and the ground plane and / or the sub-wave director element. It is characterized by: [Effects of the Invention]

[0013] In the present invention, the insulating substrate is annularly surrounded by the primary waveguide element, ground plane, and secondary waveguide element to increase the inductance La. Since the resistance value in the inductive reactance equation XL=2πfLa increases, the Q value of the series resonant circuit decreases based on the resistance value, resulting in a wider bandwidth and an RF tag antenna and RF tag that can operate over a wide frequency band. In addition, f0 can be adjusted to a low value by placing a frequency adjustment capacitor in a position parallel to the IC chip.

[0014] Furthermore, by changing the area of ​​the portion where the sub-wavedirection element overlaps with the ground plane via the coating layer, the capacitance of the capacitor can be adjusted, and thus the resonant frequency can be adjusted. The RF tag can be attached to a conductor using an adhesive layer made of insulating material. In this case, a coupling capacitance capacitor is formed consisting of the ground plane, sub-directive element, adhesive layer, and conductor, so that the conductor can be used as a director due to the capacitive coupling effect. By providing a notch on the side edge of the main wave element, it is possible to adjust the wavelength of the radio waves transmitted from the reading device and received by the main wave element. [Brief explanation of the drawings]

[0015] [Figure 1] 1(a) to (c) are perspective views showing the structure of an RF tag antenna and an RF tag, and FIG. 1(d) is an enlarged front view of the circled area in FIG. 1(c). [Figure 2] RF tag equivalent circuit diagram [Figure 3] Equivalent circuit diagrams of an RF tag without a frequency adjustment capacitor (a) and (b) [Figure 4] Graph showing the radio wave frequency and reading distance of RF tag antennas [Figure 5] (a) is a perspective view and (b) is a front view showing the RF tag installed on a conductor. [Figure 6] Equivalent circuit diagram of an RF tag placed on a conductor [Figure 7] 6A is a plan view showing the structure of an RF tag antenna according to a second embodiment; FIG. 6B is a front view showing the structure of an RF tag; and FIG. 6C is an enlarged front view of the circled area in FIG. 6B. [Figure 8] 10A and 10B are equivalent circuit diagrams of an RF tag according to a second embodiment; [Figure 9] 9(a) is a plan view showing the structure of an RF tag antenna according to a third embodiment, and FIG. 9(b) is an enlarged plan view of the circled area in FIG. 9(a). [Figure 10] 10(a) is a plan view showing the structure of an RF tag antenna according to a fourth embodiment, and FIG. 10(b) is an enlarged plan view of the circled area in FIG. 10(a). [Figure 11] Equivalent circuit diagram of the RF tag according to the fourth embodiment [Figure 12] 10A and 10B are plan views of an RF tag antenna according to a fifth embodiment; [Figure 13] 13A and 13B are plan views of a modified example of the RF tag antenna according to the fifth embodiment; [Figure 14] 1A to 1F show modified examples of an RF tag antenna and an RF tag. DETAILED DESCRIPTION OF THE INVENTION

[0016] [First embodiment] A first embodiment of an RF tag antenna and an RF tag according to the present invention will be described with reference to the drawings. 1 and 2, the RF tag antenna 1 includes an insulating substrate 10, a main waveguide element 20, a ground plane 30, a secondary waveguide element 40, a coating layer 70 made of an insulating material, and a frequency adjustment capacitor 203. The main waveguide element 20, the ground plane 30, and the secondary waveguide element 40 are formed on the surface of the coating layer 70. The RF tag 2 is configured by attaching an IC chip 60 to the RF tag antenna 1.

[0017] The insulating substrate 10 has a front surface 11, a back surface 12, and side surfaces 13. The shape of the insulating substrate 10 is, for example, a substantially rectangular parallelepiped, but is not limited to this and may be, for example, a disk-like or arc-shaped curved shape. The insulating substrate 10 preferably has a shape that corresponds to the surface shape of the object to which the RF tag 2 is to be attached. For example, if the object to be attached is cylindrical and the RF tag 2 is to be attached to its curved surface, it is preferable that the shape of the RF tag 2 matches the curvature of the curved surface. The insulating substrate 10 may be made of polystyrene foam, polyethylene, polyimide, or the like. Alternatively, the insulating substrate 10 may be made of a dielectric material such as ceramic, paper, or resin.

[0018] The main waveguide element 20 is provided on the surface 11 of the insulating substrate 10. The main waveguide element 20 of this embodiment has a rectangular shape, and is formed by a known method such as etching a thin metal film such as aluminum or pattern printing. The ground plane 30 is electrically connected to the main waveguide element 20 and is provided on the rear surface 12 of the insulating substrate 10. The ground plane 30 in this embodiment has a rectangular shape, and like the main waveguide element 20, is formed on the surface of the coating layer 70 by a well-known method such as etching a metal thin film made of aluminum or the like or pattern printing.

[0019] 1(a) and 1(d), the secondary waveguide element 40 is not directly (physically) connected to the primary waveguide element 20, i.e., the edges are disconnected. A protrusion 41 is provided on a part of the side edge of the secondary waveguide element 40, and a protrusion 23 is provided on a part of the side edge of the primary waveguide element 20. One terminal of the IC chip 60 is connected to the protrusion 41, and the other terminal is connected to the protrusion 23 of the primary waveguide element 20, thereby connecting the secondary waveguide element 40 and the primary waveguide element 20 via the IC chip 60. Note that both terminals of the IC chip 60 may be connected directly to the secondary waveguide element 40 and the primary waveguide element 20 without providing the protrusions 23 and 41. 1(b), the coating layer 70 is folded at the side of the insulating substrate 10 (see arrows) and attached to the insulating substrate 10 via an adhesive layer (not shown). As a result, as shown in FIGS. 1(c) and 1(d), at least a portion of the auxiliary waveguide element 40 overlaps with the ground plane 30 via the coating layer 70, and the auxiliary waveguide element 40, the coating layer 70, and the ground plane 30 form a capacitor 80 (see FIG. 2).

[0020] In this embodiment, the main waveguide element 20, the base plate 30, and the secondary waveguide element 40 are formed on the surface of the coating layer 70, but the coating layer 70 only needs to be present in the area where the secondary waveguide element 40 overlaps with the base plate 30. As will be described in detail later, the resonant frequency can be adjusted by changing the area of ​​the portion where the secondary waveguide element 40 overlaps with the base plate 30 via the coating layer 70. The material of the coating layer 70 is not particularly limited as long as it is flexible and insulating, and may be, for example, PET, polyimide, vinyl, etc. The thickness of the coating layer 70 is not particularly limited, but is generally about several tens of μm. The main waveguide element 20, the ground plane 30, and the secondary waveguide element 40 surround the insulating substrate 10 in an annular shape.

[0021] The main wave element 20 is preferably designed so that the total length L of its side edges 21a to 21i is any one of λ / 4, λ / 2, 3λ / 4, and 5λ / 8, where λ is the wavelength of the radio wave transmitted from the reading device. In this embodiment, the length of the side edge is adjusted to be large by providing a notch 22 in the side edge of the main wave element 20. The main wave element 20 may also be configured without the notch 22.

[0022] The frequency adjusting capacitor 203 is provided between the primary waveguide element 20 and the secondary waveguide element 40 . The frequency adjusting capacitor 203 of this embodiment is composed of a frequency adjusting element 200 having an insulating layer 201 and a conductive layer 202 . The insulator layer 201 is made of an insulator and is placed between the main waveguide element 20 and the secondary waveguide element 40. A conductor layer 202 is placed on the insulator layer 201. The conductor layer 202 needs to be long enough to overlap with the main waveguide element 20 and the secondary waveguide element 40. As a result, the upper part of the insulator layer 201 is covered with the conductor layer 202, and part of the lower part of the insulator layer 201 is covered with the main waveguide element 20 and the secondary waveguide element 40, thereby forming a frequency adjustment capacitor 203.

[0023] The IC chip 60 operates based on the radio waves received by the RF tag antenna 1. Specifically, the IC chip 60 rectifies a portion of the carrier waves transmitted from the reader and generates the power supply voltage required for operation. The generated power supply voltage is then used by the IC chip 60 to operate the control logic circuit within the IC chip 60 and the non-volatile memory that stores product-specific information, etc., and to operate the communication circuit for transmitting and receiving data to and from the reader.

[0024] Next, the configuration of an RF tag antenna without the frequency adjustment capacitor 203, that is, the configuration of an RF tag antenna in which the frequency adjustment capacitor 203 is removed from the configuration of FIG. 1, will be described. In an RF tag antenna that does not have a frequency adjustment capacitor 203, a resonant circuit is configured to resonate in the frequency band of the radio waves to be received. This resonant circuit is configured with an inductor pattern, a capacitor 80, and an IC chip 60, as shown in the equivalent circuit diagram of Figure 3. The inductor pattern is configured with a primary waveguide element 20 and a ground plane 30. The primary waveguide element 20 and the secondary waveguide element 40 are connected by the equivalent capacitance of the IC chip 60. The capacitor 80 is composed of the sub-waveguide element 40, the coating layer 70, and the ground plane 30 as described above.

[0025] Some IC chips 60 include a capacitor therein, and the IC chips 60 have stray capacitance. Therefore, when setting the resonant frequency of the resonant circuit, it is preferable to take into consideration the equivalent capacitance within the IC chip 60. In other words, it is preferable that the resonant circuit has a resonant frequency that is set in consideration of the inductance of the inductor pattern L, the capacitance of the capacitor 80, and the equivalent capacitance within the IC chip 60. The resonant frequency f0 [Hz] of this series resonant circuit is given by the following equation (1): The value of the resonant frequency f0 is preferably set to be approximately the center value of the frequency bandwidth of the multiple radio waves transmitted from the reader.

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[0026] In this way, by taking into account the equivalent capacitance inside the IC chip 60, the resonant frequency f0 of the resonant circuit can be set accurately to the frequency band of the radio waves, thereby improving the reading performance of the RF tag 2. In addition, the power supply voltage generated by the IC chip 60 can be increased. 3(b) shows a case where the area of ​​the portion where the auxiliary waveguide element 40 overlaps with the ground plane 30 via the coating layer 70 is relatively large (see the circled area in FIG. 3(b)). In this way, by changing the area of ​​the portion where the auxiliary waveguide element 40 overlaps with the ground plane 30 via the coating layer 70, it is possible to adjust Ca and thereby adjust the resonant frequency f0.

[0027] In addition, in an RF tag antenna that does not include the frequency adjustment capacitor 203, the inductance La can be increased by annularly surrounding the insulating substrate 10 with the primary waveguide element 20, the ground plane 30, and the secondary waveguide element 40. L =2πfLa, the resistance value increases and the Q value of the series resonant circuit decreases based on the resistance value, resulting in a wider bandwidth and an RF tag antenna and RF tag that can operate over a wide frequency band. Increasing the inductance La increases the impedance and lowers the resonant frequency. As a result, it becomes difficult to tune to the target resonant frequency f0. However, by setting the capacitance C, which combines the capacitance Ca of the capacitor 80 and the equivalent capacitance Cb within the IC chip 60, C = 1 / Ca + 1 / Cb, the capacitance becomes smaller, making it possible to tune to the target resonant frequency f0.

[0028] As shown in FIGS. 1 and 2, the RF tag antenna 1 of the present invention is characterized in that it includes a frequency adjusting capacitor 203 (frequency adjusting element 200). When the dimensions of the insulating substrate 10 are reduced to miniaturize the RF tag, the main waveguide element 20 and the ground plane 30 that constitute the inductor pattern L also become smaller. As a result, the frequency f0 in the above formula (1) becomes higher, which may deviate from the desired frequency band. Therefore, by providing a frequency adjusting capacitor 203 in a position parallel to the IC chip 60, the resonance frequency f0 [Hz] is given by equation (2), and f0 can be adjusted to a low value.

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[0029] In addition, in Japanese Patent No. 6705116 of the present applicant, both ends of the short-circuited portion are electrically connected to the first and second waveguide elements to form a planar inverted-F antenna (see FIG. 4C of Japanese Patent No. 6705116). On the other hand, in the RF tag antenna 5 of this embodiment, an insulator layer 201 is placed across the primary waveguide element 20 and the secondary waveguide element 40, and a conductor layer 202 is placed on top of that. In other words, it should be noted that the conductor layer 202 is not electrically connected to the primary waveguide element 20 and the secondary waveguide element 40, and the RF tag antenna 5 does not form a planar inverted-F antenna.

[0030] Figure 4 is a graph showing the radio wave frequency (horizontal axis) and reading distance (vertical axis) of the RF tag antenna 1. As a result of lowering the Q value and widening the bandwidth, it can be seen that a single RF tag 2 can handle two frequency bands: the low frequency side (around 860 MHz) used mainly in Europe, and the high frequency side (around 920 MHz) used mainly in Japan.

[0031] The RF tag 2 attached to the conductor 100 will be described with reference to FIGS. The RF tag 2 of the present invention can be used as it is, or can be used by contacting it with a conductor 100. Specifically, the back side of the RF tag 2 can be attached to the conductor 100 using an adhesive layer 101 made of an insulating material. In this application, the term "conductor" is the same as its general dictionary meaning: "a general term for a substance with a relatively high electrical conductivity," with metal being a typical example. However, the term "conductor" is not limited to metal, and may also be, for example, the human body, grass, trees, water, the ground, etc.

[0032] By attaching the RF tag 2 to the conductor 100 using the adhesive layer 101, a capacitor 81 with a coupling capacitance C is formed, which is made up of the ground plane 30, the sub-wavedirection element 40, the adhesive layer 101, and the conductor 100, and the conductor 100 can be used as a director due to the capacitive coupling effect. In this case, as shown in Fig. 5, the RF tag 2 can receive not only radio waves that reach the front side of the conductor 100, but also radio waves that reach the back side of the conductor 100. The "front side of the conductor" line in Fig. 4 shows the case where radio waves that reach the front side of the conductor 100 are read, and the "back side of the conductor" line shows the case where radio waves that reach the back side of the conductor 100 are read.

[0033] [Second embodiment] A second embodiment of the RF tag antenna and RF tag of the present invention will be described with reference to the drawings, but parts having the same configuration as those of the first embodiment will be given the same reference numerals and their description will be omitted. 7 and 8, the RF tag antenna 3 of this embodiment connects the secondary waveguide element 40 and the ground plane 30 via an IC chip 60. The antenna 3 is characterized in that at least a portion of the secondary waveguide element 40 overlaps with the primary waveguide element 20 via a coating layer 70, thereby forming a capacitor 82 by the secondary waveguide element 40, the coating layer 70, and the primary waveguide element 20. The main waveguide element 20, the ground plane 30, and the secondary waveguide element 40 surround the insulating substrate 10 in an annular shape. The frequency adjustment capacitor 203 is provided between the ground plane 30 and the sub-directive element 40. The resonant frequency can be adjusted by changing the area of ​​the portion where the secondary waveguide element 40 overlaps with the primary waveguide element 20 via the coating layer 70 .

[0034] In the RF tag antenna 3, a resonant circuit is configured to resonate in the frequency band of the radio waves to be received. This resonant circuit is configured with an inductor pattern, a capacitor 82, a frequency adjustment capacitor 203, and an IC chip 60, as shown in the equivalent circuit diagram of Fig. 8. The inductor pattern is configured with a primary waveguide element 20 and a ground plane 30. The secondary waveguide element 40 and the ground plane 30 are connected by the equivalent capacitance of the IC chip 60. The capacitor 82 is comprised of the secondary waveguide element 40, the cladding layer 70 and the primary waveguide element 20 as described above.

[0035] In the present invention, the inductance La is increased by surrounding the insulating substrate 10 in an annular shape with the main waveguide element 20, the ground plane 30, and the sub-directive element 40. L =2πfLa, the resistance value increases and the Q value of the series resonant circuit decreases based on the resistance value, resulting in a wider bandwidth and an RF tag antenna 3 and an RF tag 4 that operate over a wide frequency band. 8(b) shows a case where the area of ​​the portion where the secondary waveguide element 40 overlaps with the primary waveguide element 20 via the coating layer 70 is relatively large (see the circled area in FIG. 8(b)). In this way, by changing the area of ​​the portion where the secondary waveguide element 40 overlaps with the primary waveguide element 20 via the coating layer 70, it is possible to adjust Ca in the above formula (2) and thereby adjust the resonant frequency f0.

[0036] [Third embodiment] A third embodiment of the RF tag antenna and RF tag of the present invention will be described with reference to the drawings. The same reference numerals will be used to designate parts having the same configuration as those of the above-described embodiments, and the description thereof will be omitted. As shown in FIG. 9, this embodiment is characterized in that the frequency adjustment capacitor 203 is composed of a first extension piece 204 extending from the end of the main waveguide element 20 toward the secondary waveguide element 40, a second extension piece 205 facing the first extension piece 204 and extending from the end of the secondary waveguide element 40 toward the main waveguide element 20, and a gap 206 formed between the tip of the first extension piece and the tip of the second extension piece.

[0037] Specifically, the first extension piece 204 is T-shaped and is composed of a base portion 204a extending from the end of the main waveguide element 20 toward the secondary waveguide element 40, and a tip portion 204b extending from the tip of the base portion 204a in a direction perpendicular to the base portion 204a. The second extension piece 205 is also T-shaped and is composed of a base portion 205a extending from the end of the secondary waveguide element 40 toward the primary waveguide element 20, and a tip portion 205b extending from the tip of the base portion 205a in a direction perpendicular to the base portion 205a. The two tip portions 204b and 205b are arranged parallel to each other with a gap 206 therebetween. The first extension piece and the second extension piece are formed by a known method such as etching a thin metal film such as aluminum or pattern printing. A capacitor is formed by the two tip portions 204b, 205b and the gap 206. By providing the frequency adjustment capacitor in a position parallel to the IC chip 60, the resonance frequency f0 [Hz] is given by the above formula (2), and f0 can be adjusted to a low value. In addition, by changing the length of the tip portions 204b, 205b and the width of the gap 206, the capacitance C C can be changed to adjust f0.

[0038] [Fourth embodiment] A fourth embodiment of the RF tag antenna and RF tag of the present invention will be described with reference to the drawings. The same reference numerals will be used to designate parts having the same configuration as those of the above-described embodiments, and the description thereof will be omitted. As shown in FIG. 10, this embodiment is characterized in that the frequency adjustment capacitor is composed of an island-shaped piece 207 arranged in an island shape between the main waveguide element 20 and the secondary waveguide element 40, and gaps 208a to 208d formed between the island-shaped piece 207 and the main waveguide element 20 and the secondary waveguide element 40. The island-like pieces 207 are formed by a known method such as etching a thin metal film such as aluminum or pattern printing.

[0039] In this embodiment, two island pieces 207 are arranged with the IC chip 60 sandwiched between them, thereby forming four gaps 208a to 208d, which form four capacitors 209a to 209d as frequency adjustment capacitors as shown in Figure 11. In this case, the capacitance C dis given by equation (3). By providing a frequency adjustment capacitor in a position parallel to the IC chip 60, the resonance frequency f0 [Hz] is given by equation (4), and f0 can be adjusted to a low value. In addition, by changing the length and width of the island-shaped piece 207 and the width of the gaps 208a to 208d, the capacitance C d can be changed to adjust f0. It is to be noted that only one island-shaped piece 207 may be disposed, or three or more may be disposed.

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[0040] [Fifth embodiment] A fourth embodiment of the RF tag antenna and RF tag of the present invention will be described with reference to the drawings. The same reference numerals will be used to designate parts having the same configuration as those of the above-described embodiments, and the description thereof will be omitted. As shown in FIG. 12(a), in this embodiment, an L-shaped slit 42 is provided in a part of the secondary waveguide element 40 to form a tongue-shaped piece 210, and the base of the tongue-shaped piece 210 is bent at the dotted line and joined to the back surface of the main waveguide element 20 via an insulator to insulate the main waveguide element 20 from the tongue-shaped piece 210, as shown in FIG. 12(b), to form a frequency adjustment capacitor. The frequency adjustment capacitor is composed of a primary waveguide element 20, a secondary waveguide element 40, a coating layer 70 made of an insulating material, and a tongue-shaped piece 210.

[0041] Furthermore, although not shown in the figures, a tongue-shaped piece may be formed by providing a slit in a part of the main waveguide element 20, and the base of the tongue-shaped piece may be bent and joined to the back surface of the secondary waveguide element 40 via an insulator to insulate the secondary waveguide element 40 from the tongue-shaped piece, thereby forming a frequency adjustment capacitor. Alternatively, as shown in FIG. 13(a), a tongue-shaped piece 210 may be formed by providing an L-shaped slit 42 in a part of the secondary waveguide element 40, and the base of the tongue-shaped piece 210 may be bent at the dotted line and joined to the back surface of the base plate 30 via an insulator to insulate the base plate 30 from the tongue-shaped piece 210, as shown in FIG. 13(b), to form a frequency adjustment capacitor. The frequency adjustment capacitor is composed of a ground plane 30, a sub-directive element 40, a coating layer 70 made of an insulating material, and a tongue-shaped piece 210. Alternatively, a tongue-shaped piece may be formed by providing a slit in part of the base plate 30, and the base of the tongue-shaped piece may be bent and joined to the rear surface of the sub-wave director element 40 to form a frequency adjustment capacitor.

[0042] [Fourth embodiment] FIG. 14 shows a comprehensive list of modified examples of the RF tag antenna and RF tag of the present invention. Figure 14(a) shows a configuration in which the secondary director element 40, the primary director element 20, and the ground plane 30 are wrapped around the insulating substrate 10 with the coating layer 70 in contact with the insulating substrate 10, and the surface of the secondary director element 40 is covered with part of the ground plane 30. Figure 14(b) shows a configuration in which the secondary waveguide element 40, the ground plane 30, and the main waveguide element 20 are wrapped around the insulating substrate 10 with the coating layer 70 in contact with the insulating substrate 10, and the surface of the secondary waveguide element 40 is covered with part of the main waveguide element 20. 14(c) shows a configuration in which the coating layer 70 is exposed to the outside, that is, turned upside down from the state shown in FIG. 1(a), the main waveguide element 20 and the ground plane 30 are wrapped around the insulating substrate 10, and part of the surface of the ground plane 30 is covered with the sub-directive element 40. In this configuration, the IC chip 60 is not exposed to the outside, which reduces the risk of damage. 14(d) shows a configuration in which the main waveguide element 20 and the ground plane 30 are wrapped around the insulating substrate 10 with the coating layer 70 exposed to the outside, and part of the surface of the main waveguide element 20 is covered with the secondary waveguide element 40. Figure 14(e) shows a configuration in which the secondary waveguide element 40, the primary waveguide element 20, and the ground plane 30 are wrapped around the insulating substrate 10 with the coating layer 70 exposed to the outside, and the surface of the secondary waveguide element 40 is covered with part of the ground plane 30. Figure 14(f) shows a configuration in which the secondary waveguide element 40, the ground plane 30, and the main waveguide element 20 are wrapped around the insulating substrate 10 with the coating layer 70 exposed to the outside, and the surface of the secondary waveguide element 40 is covered with part of the main waveguide element 20. 14(a) to 14(f) can provide an RF tag antenna and an RF tag that operate over a wide frequency band. Note that a frequency adjustment capacitor is provided in each of the configurations in FIG. [Industrial Applicability]

[0043] The present invention is an antenna for an RF tag that operates over a wide frequency band and has industrial applicability. [Explanation of symbols]

[0044] 1 RF tag antenna 2. RF tag 3 RF tag antenna 4. RF tag 5 RF tag antenna 6. RF tags 10. Insulating substrate 11 Surface 12 Back side 13 Side 20 Main Wave Element 21a~21i side 22 Cut 23 Convex part 30 Main plate 40 Sub-waveguide element 41 Convex part 42 Slit 60 IC chips 70 Coating layer 80 capacitors 81 Capacitor 82 Capacitor 100 conductors 101 Adhesive layer 200 Frequency Adjustment Element 201 Insulator Layer 202 Conductive layer 203 Frequency adjustment capacitor 204 1st extension piece 204a base 204b Tip 205 2nd extension piece 205a base 205b Tip 206 Gap 207 Island piece 208a~208d Gap 209a~209d Capacitors 210 Lingulae

Claims

1. The device includes an insulating substrate, a primary waveguide element, a ground plane electrically connected to the primary waveguide element, a secondary waveguide element connected to the primary waveguide element via an IC chip, and a frequency adjustment capacitor, the main waveguide element is provided on a surface of the insulating substrate, and the ground plane is provided on a back surface of the insulating substrate; at least a portion of the auxiliary waveguide element overlaps with the ground plane via a coating layer made of an insulating material, whereby the auxiliary waveguide element, the coating layer, and the ground plane form a capacitor, and the insulating substrate is surrounded by the main waveguide element, the ground plane, and the auxiliary waveguide element in an annular shape; the frequency adjustment capacitor is provided between the primary waveguide element and the secondary waveguide element, An antenna for an RF tag, characterized in that the frequency adjustment capacitor is composed of a first extension piece extending from the end of the main waveguide element toward the secondary waveguide element, a second extension piece facing the first extension piece and extending from the end of the secondary waveguide element toward the main waveguide element, and a gap formed between the tip of the first extension piece and the tip of the second extension piece.

2. The device includes an insulating substrate, a primary waveguide element, a ground plane electrically connected to the primary waveguide element, a secondary waveguide element connected to the primary waveguide element via an IC chip, and a frequency adjustment capacitor, the main waveguide element is provided on a surface of the insulating substrate, and the ground plane is provided on a back surface of the insulating substrate; at least a portion of the auxiliary waveguide element overlaps with the ground plane via a coating layer made of an insulating material, whereby the auxiliary waveguide element, the coating layer, and the ground plane form a capacitor, and the insulating substrate is surrounded by the main waveguide element, the ground plane, and the auxiliary waveguide element in an annular shape; the frequency adjustment capacitor is provided between the primary waveguide element and the secondary waveguide element, An antenna for an RF tag, characterized in that the frequency adjustment capacitor is composed of an island-shaped piece arranged in an island shape between the main waveguide element and the secondary waveguide element, and gaps formed between the island-shaped piece and the main waveguide element and between the island-shaped piece and the secondary waveguide element.

3. The device includes an insulating substrate, a primary waveguide element, a ground plane electrically connected to the primary waveguide element, a secondary waveguide element connected to the ground plane via an IC chip, and a frequency adjustment capacitor, the main waveguide element is provided on a surface of the insulating substrate, and the ground plane is provided on a back surface of the insulating substrate; At least a part of the secondary waveguide element overlaps with the primary waveguide element via a coating layer made of an insulating material, whereby the secondary waveguide element, the coating layer, and the primary waveguide element form a capacitor, and the primary waveguide element, the ground plane, and the secondary waveguide element surround the insulating substrate in an annular shape, The RF tag antenna is characterized in that the frequency adjustment capacitor is provided between the ground plate and the sub-wave director element.

4. The frequency adjustment capacitor is composed of a frequency adjustment element consisting of an insulating layer and a conductive layer, the insulating layer is disposed between the ground plane and the auxiliary waveguide element; 4. The RF tag antenna according to claim 3, wherein the conductive layer is disposed on the insulating layer.

5. An antenna for an RF tag as described in Claim 3, characterized in that the frequency adjustment capacitor is composed of a first extension piece extending from the end of the base plate toward the secondary waveguide element, a second extension piece extending from the end of the secondary waveguide element opposite the first extension piece toward the primary waveguide element, and a gap formed between the tip of the first extension piece and the tip of the second extension piece.

6. An antenna for an RF tag as described in Claim 3, characterized in that the frequency adjustment capacitor is composed of an island-shaped piece arranged in an island shape between the ground plate and the secondary waveguide element, and a gap formed between the island-shaped piece and the ground plate and / or the secondary waveguide element.

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