JP2017102789A - Polarization-free IC tag - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polarization-free IC tag capable of communication at an excellent sensitivity state regardless of a type of polarization of an antenna of a reader/writer device in battery-less passive IC tags.SOLUTION: A polarization-free IC tag comprises: a patch antenna 3 including a nearly rectangular antenna element 4, a power supply point fand a power supply point fbeing provided at different points of the antenna element 4; an IC tag unit 6 electrically connected with the power supply point f; and an IC tag unit 8 electrically connected with the power supply point f. The antenna element 4 is provided with notches 12 and 13 at respective opposite corners on one diagonal line.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a polarization-free IC tag.

  In recent years, there is a growing demand for increasing the sensitivity of passive IC tags. In communication between an IC tag and a reader / writer device, it is known that the IC tag has good sensitivity when the polarizations of antennas incorporated in the IC tag and the reader / writer device match. The polarization of an antenna includes linear polarization in which an electric field always exists in one plane and circular polarization in which an electromagnetic field rotates in the propagation direction (see Patent Document 1 below). Among circularly polarized waves, a circularly polarized wave whose electromagnetic field rotates to the right (turning right) in the direction of radio wave propagation is called a right-turning circularly polarized wave, and a circularly polarized wave that rotates left (turns left). This is called left-turn circular polarization.

  For example, when the polarization of the antenna of the IC tag is a linear polarization and the polarization of the antenna of the reader / writer device is a circular polarization, the circular polarization generated by the antenna of the reader / writer device is changed to a linear polarization. When transmitted to the antenna of the IC tag to be generated, approximately half of the rotating polarization is communicated as a component that matches the linear polarization of the IC tag.

  In addition, when the polarization of the antenna of the IC tag is a circular polarization and the polarization of the antenna of the reader / writer device is a circular polarization, the circular polarization of both antennas facing each other is a right-handed circular polarization. There is a good sensitivity when both are left-handed circularly polarized waves, that is, when the polarization directions of the circularly polarized waves are the same in the same rotation direction.

Japanese Patent Laying-Open No. 2015-164258

  However, when the polarization of the antenna of the IC tag is a linear polarization and the polarization of the antenna of the reader / writer device is a circular polarization, approximately half of the rotating polarization matches the linear polarization of the IC tag. As a result, half of the radio wave energy is wasted.

  Further, when the polarization of the antenna of the IC tag is a circular polarization and the polarization of the antenna of the reader / writer device is a circular polarization, the antenna polarization of the IC tag is a linear polarization and the reader / writer device Although the problem of wasteful radio wave energy consumption as in the case where the antenna polarization is circular polarization is solved, the following problems arise.

  That is, there is a case where the lowest sensitivity or no response occurs when the polarization directions of the two circularly polarized waves do not match. For example, when the circular polarization of the antenna of the reader / writer device communicated with an IC tag having an antenna that generates a left-handed circularly polarized wave is a right-handed circularly polarized wave, communication itself cannot be performed. In particular, when the distribution across companies, for example, a distribution container with an IC tag attached is exported overseas, the polarization direction of the circular polarization of the antenna of the reader / writer device at the export destination is unknown. In this case, there is a risk that the information stored in the IC tag at the export destination cannot be read.

  The present invention relates to a battery-less passive IC tag, which is a polarization-free IC tag capable of performing communication in a good sensitivity state regardless of the type of polarization of an antenna of a reader / writer device, in particular, the direction of rotation of circularly polarized waves. Is to provide.

  In order to solve the above problems, a polarization-free IC tag according to the present invention includes a patch antenna having a substantially rectangular antenna element, and a first feeding point and a second feeding point at different positions of the antenna element. A first IC tag portion formed and electrically connected to the first feeding point; and a second IC tag portion electrically connected to the second feeding point; A notch is formed in each of the opposing corners on the diagonal line.

  In the above-described invention, the first feeding point is formed at a position away from the first edge of the antenna element by a predetermined distance from the first edge toward the center in a direction perpendicular to the first edge. The feeding point of 2 is centered in a direction perpendicular to any one of the second edge parts from two second edge parts perpendicularly adjacent to the first edge part of the antenna element. It is preferable that it is formed at a position separated by a predetermined distance toward.

  In the above-described invention, the first feeding point is on a straight line extending in a direction perpendicular to the first edge of the antenna element and toward the center of the antenna element, and extending from the first edge to the antenna element. The second feed point is formed adjacent to the first edge of the antenna element at a right angle 2 at a predetermined distance from a position half the length to the center toward the center of the antenna element. The length from the second edge to the center of the antenna element is a straight line extending in a direction perpendicular to any one of the two second edges and toward the center of the antenna element. Preferably, it is formed at a position away from the half position by a predetermined distance toward the vicinity of the center excluding the center of the antenna element.

  In the above-described invention, the first feeding point is on a straight line extending in a direction perpendicular to the first edge of the antenna element and toward the center of the antenna element, and extending from the first edge to the antenna element. The second feed point is formed adjacent to the first edge of the antenna element at a right angle 2 at a predetermined distance from the half of the length to the center toward the first edge. The length from the second edge to the center of the antenna element is a straight line extending in a direction perpendicular to any one of the two second edges and toward the center of the antenna element. It is preferable to form it at a position away from the half position by a predetermined distance toward the second edge.

  In the above-described invention, the first feeding point is a position separated from the first edge of the antenna element by a distance that is half the length of the edge in the direction perpendicular to the first edge toward the center. The second feed point is formed at a predetermined distance from the second edge adjacent to the first edge of the antenna element toward the center in a direction perpendicular to the second edge. It is preferable that they are formed at different positions. Here, the predetermined distance is an adjustment distance for matching the antenna impedance of the feeding point. In electromagnetism, a distance that is half the shortest length between the edge and the center is preferable. It is known that when the antenna impedance is adjusted to be high, the feeding point is formed near the edge, and when it is adjusted to be low, it is formed at a position closer to the center.

  In the above-described invention, two IC chips are arranged at two feeding points of one patch antenna, respectively, so that it has a function of transmitting / receiving either left-turn circular polarization or right-turn circular polarization. Is preferred.

  In the above-described invention, each of the first IC tag portion and the second IC tag portion is disposed at a position facing the IC chip, the first antenna connected to the IC chip, and the first antenna. And a second antenna electrically connected to a ground plate constituting the patch antenna.

  In the above-described invention, at least the first antenna and the second antenna are arranged close to each other so as to be capable of electromagnetic inductive coupling and are opposed to each other so as to induce mutual electromagnetic induction between the two loop coils. The antenna is a loop coil, and a first through hole formed in a dielectric substrate in which one end of the second antenna corresponding to the first IC tag portion is connected to the ground plate and the other end is laminated on the ground plate. Through the second through hole connected to the first feeding point, one end of the second antenna corresponding to the second IC tag portion connected to the ground plate, and the other end formed in the dielectric substrate. It is preferably connected to the second feed point.

  ADVANTAGE OF THE INVENTION According to this invention, the polarization free IC tag which can communicate in a favorable sensitivity state irrespective of the kind of polarization of the antenna of a reader / writer apparatus can be provided.

It is a perspective view which shows the external appearance of a polarization free IC tag. It is a figure for demonstrating the relationship between the position of two feeding points of a patch antenna, and antenna impedance (feeding point impedance). It is a figure for demonstrating the formation of the structure of the patch antenna which comprises a polarization free IC tag. It is a figure for demonstrating the principle that a circularly polarized wave generate | occur | produces with a patch antenna. It is a partial transmission top view for demonstrating the connection of the feeding point of a patch antenna, and an electromagnetic coupling coil. It is the sectional view on the AA line of FIG. FIG. 2 is a detailed cross-sectional view taken along line AA in FIG. 1. It is the BB sectional view taken on the line of FIG. It is a BB sectional detail drawing of FIG. It is the front view which showed the IC tag part incorporated in the polarization free IC tag.

  Hereinafter, a polarization-free IC tag according to an embodiment of the present invention will be described with reference to the drawings.

[Configuration of polarization-free IC tag]
FIG. 1 is a perspective view showing the appearance of a polarization-free IC tag. FIG. 2 is a diagram for explaining the relationship between the positions of the two feeding points of the patch antenna and the antenna impedance (feeding point impedance). FIG. 3 is a diagram for explaining that the structure of the patch antenna that constitutes the polarization-free IC tag can be integrated into one by adding the respective occurrences of left and right circularly polarized waves. FIG. 4 is a diagram for explaining the principle that circularly polarized waves are generated in the patch antenna in the direction of the high-frequency current, and represents a case of left turn as a representative. FIG. 5 is a partially transparent plan view for explaining the connection between the feeding point of the patch antenna and the electromagnetic coupling coil. 6 is a cross-sectional view taken along line AA in FIG. FIG. 7 is a detailed sectional view taken along line AA in FIG. 8 is a cross-sectional view taken along line BB in FIG. FIG. 9 is a detailed sectional view taken along line BB in FIG. FIG. 10 is a front view showing the IC tag unit 6 and the IC tag unit 8.

  As shown in FIG. 1, the polarization-free IC tag 1 includes a ground plate (ground conductor) 11, a printed board (dielectric) 9 placed on the ground board 11, and a ground board 11 with the printed board 9 interposed therebetween. Antenna element (antenna pattern) 4 disposed substantially parallel to the antenna element 4 and IC tag portions 6 and 8 (see FIGS. 7 and 9) disposed on the antenna element 4 and including the IC tags 5 and 7, respectively. Configured. Finally, as shown in FIGS. 6 and 8, the cover body 40 is fixed to the ground plate 11 with screws 42 so as to cover the entire polarization-free IC tag 1. The printed circuit board corresponds to the “dielectric substrate” recited in claim 7. That is, the polarization free IC tag 1 includes two IC tags 5 and an IC tag 7 therein.

[Patch antenna]
The patch antenna 3 includes a substantially rectangular antenna element 4, a printed board 9, and a ground plate 11 that is electrically connected to the antenna element 4 through the printed board 9. The patch antenna 3 has a function of transmitting / receiving a signal to / from an external reader / writer device (not shown) in cooperation with IC chips 30 and 35 (described later) electrically connected to the antenna element 4. Have. The antenna element 4 has a shape in which a pair of opposite corners are cut out (in the example of FIG. 2, a shape in which cutout portions 12 and 13 are formed by cutting out the upper left and lower right corners). The antenna element 4 is provided with feeding points f _R and f _{L at} desired positions where the detection direction is defined. Details of the desired feeding point position will be described later.

The above-described shape of the antenna element 4 conceptually generates a square notch shape (a shape shown in the upper left of FIG. 3) having a function of generating a left-turn circular polarization and a right-turn circular polarization. The shape is a combination of a square notch shape having a function (a shape shown on the lower left side in FIG. 3) and a shape rotated clockwise by 90 degrees. Actually, the patch antennas are not formed by combining two patch antennas, but are fed into a single patch antenna having a shape in which opposite corners are cut off at two positions to be described later, and feed points f for generating right-handed circularly polarized waves, respectively. by adding the structure of the feeding point f _L of _R and the left-handed circularly for waveguide polarizer is formed by providing to aggregate together. The feeding point f _R corresponds to the “first feeding point” described in claim 1, and the feeding point f _L corresponds to the “second feeding point” described in claim 1. Yes.

  The reason for the above-mentioned shape is that a two-corner notch shape (the shape shown in the upper left of FIG. 3) having a function of generating a left-turning circularly polarized wave and a two-way cutting having a function of generating a right-turning circularly polarized wave By combining the notch shapes (the shape shown in the lower left side of FIG. 3), either one of the left circular polarization and the right circular polarization is received. This is to ensure the best reception sensitivity as the polarization free IC tag 1 by operating without fail.

The antenna element 4 has two feeding points f _R and f _L as shown in FIG. Specifically, the antenna element 4, an electromagnetic coupling coil (loop coil) 17 connected to a feeding point f _R, respectively ground via the electromagnetic coupling coil (loop coil) 19 connected to a feeding point f _L Connected to the plate 11.

[Principle of circular polarization of patch antenna]
The shape of the antenna element 4 constituting the polarization-free IC tag according to the present invention is as described above so as to have a left-turning circular polarization generation function and a right-turning circular polarization generation function. Next, the principle of generation of left-turn circular polarization and right-turn circular polarization in the patch antenna 3 will be briefly described. First, a mechanism (principle) for generating circular polarization with a square patch antenna will be described with reference to FIG. In the patch antenna formed by cutting the upper left and lower right corners into a right-angled isosceles triangle ΔS shape having a hypotenuse of 45 degrees, the direction of the current reflected by the hypotenuse of 45 degrees of the notch is the left-right direction. The polarization plane becomes vertical, diagonal, or horizontal, and circular polarization is generated with the polarization plane rotating with time. Note that the area of the right-angled isosceles triangle ΔS that is notched is preferably set to approximately 1/150 of the area of the antenna element 4.

  Hereinafter, the principle of rotation of the polarization plane will be specifically described. The current flowing from the lower left to the upper left in (1) of FIG. 4 collides with the hypotenuse of the upper left cutout of 45 degrees, and as a result, the direction changes by 90 degrees. After that, it flows from the upper left to the upper right as shown in (2). On the other hand, the current flowing from the lower right to the upper right in (1) travels in the opposite direction by 180 degrees as shown in (2) by colliding with the upper right corner. In (2), the current from the upper left to the lower right, which is a combination of these two current vectors, flows through the entire patch antenna. Therefore, the plane of polarization is oblique. That is, the polarization plane of the patch antenna 3 is vertical in (1), is diagonal in (2), is horizontal in (3), is diagonal in (4), and the plane of polarization is (1) to (4) with time. Will change. In FIG. 4, the direction in which the current travels is indicated by an arrow, but in (2) to (4), the polarity of the high-frequency current (alternating current) is reversed, so that the current vector in (2) changes from upper left to right. If the direction is downward, the current vector in (4) changes from the lower right to the upper left. As a result, a circularly polarized wave whose polarization plane rotates is generated.

  In general, electromagnetic waves radiated from a square patch antenna without cutout are linearly polarized waves such as horizontally polarized waves and vertically polarized waves, and the polarization of the electric field plane coincides with the direction connecting the feed point and the center point. . However, as described above, circularly polarized waves are radiated by cutting away the opposite corners. For example, left-handed polarized waves can be generated by cutting out the upper left and lower right corners of the antenna element of the patch antenna (the upper left antenna in FIG. 3). On the contrary, right-handed polarized waves can be generated by cutting out the upper right and lower left corners of the antenna element of the patch antenna (the lower left antenna in FIG. 3).

  Note that the gain of the patch antenna 3 is determined by the material of the printed circuit board on which the patch antenna is formed. Generally, the lower the relative dielectric constant of the substrate, the lower the loss and the higher the gain. The ultimate material is vacuum or air. On the other hand, the higher the relative dielectric constant of the substrate, the smaller the patch antenna 3 can be made. Therefore, it is desirable to design the patch antenna 3 while keeping a balance according to the priority of gain and miniaturization.

[Relationship between the position of the feed point provided on the patch antenna and the antenna impedance]
The antenna impedance (feeding point impedance) Z _feed is usually fed directly by a 50 ohm coaxial cable. Therefore, in the following, the antenna impedance Z _feed is determined to be 50 ohms and is related to the antenna impedance Z _feed. The position of the feeding point that can secure the best sensitivity will be described.

As shown in FIG. 2, the first feeding point f _L when the antenna impedance Z _feed is 50 ohms (Ω) and the antenna shape is a pair of square notches on a square diagonal line with a width _L. position of, when the length from the edge portion 27 of the patch antenna 3 to the feed point f _L is a, the distance from the edge portion 27 of the antenna element 4 to the center O of the X axis X _C was a, the antenna element the best sensitivity from 4 edge portion 27 when the position of the half of the distance a to the center O of the X axis X _C (a-a) (i.e. L / 4).

On the other hand, the position of the second feeding point f _R is from the antenna element 4 of the edge portion 28 to the feed point f _R and the length is B, from edge portion 28 of the antenna element 4 to the center O of the Y-axis Y _C If the distance was as a, the best sensitivity when the position of the half of the distance a from the antenna element 4 of the edge portion 28 to the center O of the Y-axis Y _C (a-B) (i.e. L / 4) .

The relational expression between the position of the feeding point and the antenna impedance Z _feed is as shown in the following formula (1) known in electromagnetics, antenna engineering, and the like.
Z _feed = 50 | tan (A / L−1 / 2) π | (1)

In the above formula (1), the horizontal axis represents the position of the feeding point of the antenna (distance from the edge of the antenna), the vertical axis represents the impedance, the measured data is plotted on the graph, and the curve graph (Fig. (Not shown). When the value of the impedance (feeding impedance) of a feeding device (not shown) including the feeding point is input using Equation (1), the feeding point position (A / L) is obtained. When electromagnetic coupling is desired with an impedance Z _{feed of} 50 ohms, A / L and B / L are about 0.25, and the arrangement configuration of the feeding points f _L and f _R is as shown in FIG.

When the impedance Z _{feed is} to be electromagnetically coupled with an impedance other than 50 ohms, the relationship between the position of the feeding point and the antenna impedance Z _feed is obtained from the curve graph based on the actual measurement data, and then the position of the feeding point of the antenna. Can be requested. If electromagnetic coupling is desired with an impedance exceeding 50 ohms (Z _feed ), the feed points f _L and f _R may be brought closer to the edge side of the antenna element 4. It is known that when the feed points f _L and f _R are provided on the edge of the antenna element 4, it theoretically becomes infinitely large, but is actually about 200 ohms due to the influence of loss and the like.

As described above, the position of the feeding point is provided anywhere from the center O (center point) of the antenna element 4 to the edge, but the feeding points f _R and f _{L to} which the electromagnetic coupling coils 17 and 19 are connected. When the impedance is 50 ohms or less, it is provided between half the position from the vicinity of the center point excluding the center point O to the edge. When the impedance of the feeding point is 50 ohms, it is provided at exactly half the position (L / 4). When it exceeds 50 ohms, it is formed at a position separated by a predetermined distance from the half position from the edge to the center of the antenna element 4 toward the edge.
If the impedance of the feeding point is not known, calculation design cannot be performed, and it can be provided by experiment. The position of the feeding point by experiment can be obtained as a position where impedance matching is achieved when the position from the center point of the antenna element 4 to the edge is gradually shifted and the sensitivity is maximized.

[IC tag part]
The IC tag unit 6 shown in FIG. 7 includes a first IC tag 5 having an IC chip 30 and a coil antenna 31 and a spiral loop coil 17. The coil antenna 31 is formed so as to surround the IC chip 30, and both ends of the coil are electrically connected to the IC chip 30 via connection terminals (not shown). One end of the loop coil 17 (coil end (EP)) are electrically connected by soldering or laser welding or PCB laminate or the like to a feeding point f _R provided on the antenna pattern of the patch antenna 3. The other end of the loop coil 17 (coil start end (SP)) is electrically connected to the ground plate 11 through a through hole 20 formed in the printed circuit board 9 by soldering, laser welding, or printed circuit board lamination. (See FIGS. 6 and 7). The IC tag portion 6 corresponds to the “first IC tag portion” recited in claim 1, and the through hole 20 corresponds to the “first through hole” recited in claim 7.

The IC tag portion 8 shown in FIG. 9 includes a second IC tag 7 having an IC chip 35 and a coil antenna 37, and a spiral loop coil 19. The coil antenna 37 is formed so as to surround the IC chip 35, and both ends of the coil are electrically connected to the IC chip 35 via connection terminals (not shown). One end of the loop coil 19 (coil end (EP)) are electrically connected by soldering or laser welding or PCB laminate or the like to a feeding point f _L provided in the antenna pattern of the patch antenna 3. The other end of the loop coil 19 (coil start end (SP)) is electrically connected to the ground plate 11 through a through hole 22 formed in the printed circuit board 9 by soldering, laser welding, or printed circuit board lamination. (See FIGS. 8 and 9). The coupling coil patterns of the loop coils 17 and 19 are preferably formed with the number of turns (for example, one to several turns) that is matched at the frequency to be used and has the best sensitivity. The IC tag portion 8 corresponds to the “second IC tag portion” described in claim 1, and the through hole 22 corresponds to the “second through hole” described in claim 7. Yes.

  FIG. 10 is a front view of the IC tag unit 6 and the IC tag unit 8. As an example, an IC tag portion having a small size of 2.5 mm square such as IM5-PK2525 type manufactured by Hitachi Chemical Co., Ltd. is suitable.

  The loop coil 17 is arranged at a predetermined distance from the IC chip 30 at a position facing the coil antenna 31, and two coils are opposed to each other like a transformer by mutual electromagnetic induction coupling with the coil antenna 31 of the IC tag 5. It has a role to promote transmission of electromagnetic energy. The loop coil 19 is disposed at a predetermined distance from the IC chip 35 at a position facing the coil antenna 37, and two coils are opposed to each other like a transformer by mutual electromagnetic induction coupling with the coil antenna 37 of the IC tag 7. It has a role to promote transmission of electromagnetic energy. The coil antennas 31 and 37 correspond to the “first antenna” described in claims 6 and 7. The loop coils 17 and 19 correspond to the “second antenna” described in claims 6 and 7.

  The IC chip 30 includes a power supply circuit, a transmission / reception circuit, a memory, a logic control circuit, and the like having a function of generating electric power required by the IC chip 30 from the high-frequency current of the loop coil 17. Similarly to the above, the IC chip 35 also includes a power supply circuit, a transmission / reception circuit, a memory, a logic control circuit, and the like having a function of generating power required by the IC chip 35.

  The IC tag portions 6 and 8 which are passive tags do not have a built-in battery, but each of the IC chips obtains an induced electromotive force by mutual electromagnetic induction coupling (transformer coupling) from radio waves received by the loop coils 17 and 19, respectively. The power supply circuit composed of integrated circuits 30 and 35 operates, and the entire IC tag functions. Note that details of the configuration and operation of these components are omitted because they can be easily understood by those skilled in the art.

  The logic control circuit is configured by a CPU (Central Processing Unit), and the memory stores data such as ID (identification information). Here, tag information such as IDs to be stored is information common to the IC chips 30 and 35 for the sake of convenience of constituting one polarization-free IC tag 1 with the IC chip 30 and the IC chip 35. It may be different information.

  An advantage of using the same information is that it can function as a single IC tag and can have redundancy. An advantage of using different information is that it is possible to recognize which IC chip has failed when an IC chip fails.

  The memory includes a ROM (Read Only Memory) for storing data, a RAM (Random Access Memory), an EEPROM (Electrically Erasable Programmable Read-Only Memory), and the like. The polarization-free IC tag 1 can communicate with a reader / writer device (not shown) based on the data. For example, the memory can store, for example, information such as the specific information or position of the cargo where the IC tag is installed, communication records, and the like. Note that details of the configuration and operation of these components are omitted because they can be easily understood by those skilled in the art.

[Operation of IC tag]
In the following, when the polarization of the antenna of the reader / writer device is a circular polarization, the polarization when the circular polarization is transmitted from the reader / writer device to the polarization-free IC tag 1 configured as described above. The operation of the free IC tag will be described. When, for example, right-handed circularly polarized light is radiated from the reader / writer device, the electromagnetic induction coupled IC chip 30 functions with the best sensitivity due to electromagnetic induction between the loop coil 17 and the coil antenna 31. Further, even when, for example, counterclockwise circularly polarized waves are radiated from the reader / writer device, the electromagnetic induction coupled IC chip 35 functions with the best sensitivity due to electromagnetic induction between the loop coil 19 and the coil antenna 37. Become.

[effect]
In a conventional IC tag, when the polarization of the antenna of the reader / writer device is a circular polarization, if the polarization of the antenna of the IC tag is a linear polarization, approximately half of the rotating polarization is a straight line of the IC tag. Even if the polarized wave of the IC tag antenna is circularly polarized, the polarization directions of the two circularly polarized waves coincide with each other because half of the radio wave energy is wasted because it is a component that does not match the polarized wave. If not, it will create a case that does not respond at the lowest sensitivity or worst case.

  According to the polarization-free IC tag according to the present invention, since it has a left-turning circularly polarized antenna and a right-turning circularly polarized antenna, for example, circular polarization radiated from the antenna of the reader / writer device Communication can be performed with the best possible sensitivity regardless of whether it is a right-turn circular polarization or a left-turn circular polarization. For example, when a distribution container with an IC tag attached is exported overseas, the polarization direction of the circular polarization of the antenna of the reader / writer device at the export destination is often unknown. However, if the polarization-free IC tag according to this embodiment is attached to a distribution container, the information stored in the IC tag can be stored regardless of the circular polarization of the antenna of the reader / writer device at the export destination. Easy to read.

  Further, since the polarization-free IC tag according to the present invention is a batteryless passive IC tag, it is not necessary to replace the battery.

  Although one embodiment of the present invention has been described above, the present invention can be variously modified in addition to this. In the above-described embodiment, 920 MHz is cited as the frequency of the UHF band used in RFID communication. However, the frequency of the UHF band used in RFID communication may be any frequency as long as it is a band from 860 MHz to 960 MHz, for example. Further, the frequency used in RFID communication is not limited to the UHF band frequency, and may be a frequency centered on 2.45 GHz called a microwave or a frequency centered on 433 MHz. Other frequencies may be used.

DESCRIPTION OF SYMBOLS 1 ... Polarization free IC tag, 3 ... Patch antenna, 4 ... Antenna element (antenna pattern), 5, 7 ... IC tag, 6, 8 ... IC tag part, 9 ... Printed circuit board (dielectric), 11 ... Ground board , 17, 19 ... Electromagnetic coupling coil (loop coil), 20, 22 ... Through-hole, 27, 28 ... Edge, 30, 35 ... IC chip, 31, 37 ... Coil antenna

Claims (8)

A patch antenna having a substantially rectangular antenna element;
A first feeding point and a second feeding point are formed at different positions of the antenna element,
A first IC tag portion electrically connected to the first feeding point;
A second IC tag portion electrically connected to the second feeding point,
The antenna element is formed by forming a notch at each of opposite corners on one diagonal line,
A polarization-free IC tag characterized by the above. The first feeding point is formed at a position away from the first edge of the antenna element by a predetermined distance in the direction perpendicular to the first edge toward the center.
The second feeding point is perpendicular to one of the second edges from two second edges adjacent to the first edge of the antenna element at right angles. It is formed at a position away from the center by a predetermined distance.
The polarization-free IC tag according to claim 1. The first feeding point extends in a direction perpendicular to the first edge portion of the antenna element and is on a straight line toward the center of the antenna element, from the first edge portion to the center of the antenna element. It is formed at a position that is a predetermined distance away from a position that is half the length toward the center of the antenna element,
The second feeding point extends in a direction perpendicular to one of the two second edges adjacent to the first edge of the antenna element at a right angle, and the center of the antenna element. Is formed at a position that is a predetermined distance away from a position that is half the length from the second edge to the center of the antenna element toward the vicinity of the center excluding the center of the antenna element. The
The polarization-free IC tag according to claim 2. The first feeding point extends in a direction perpendicular to the first edge portion of the antenna element and is on a straight line toward the center of the antenna element, from the first edge portion to the center of the antenna element. Formed at a position separated by a predetermined distance from the half-length position toward the first edge,
The second feeding point extends in a direction perpendicular to one of the two second edges adjacent to the first edge of the antenna element at a right angle, and the center of the antenna element. Is formed at a position that is a predetermined distance away from the position of half the length from the second edge to the center of the antenna element toward the second edge.
The polarization-free IC tag according to claim 2. The first feeding point is located at a position separated from the first edge of the antenna element by a distance that is half the length from the edge extending in the direction perpendicular to the first edge to the center of the antenna element. Formed,
The second feeding point has a length from the second edge adjacent to the first edge of the antenna element to the center of the antenna element from the edge perpendicular to the second edge. Formed at a position separated by half the distance,
The polarization-free IC tag according to claim 1. The patch antenna has a function of transmitting and receiving left-turn circular polarization or right-turn circular polarization.
The polarization-free IC tag according to claim 1. Each of the first IC tag part and the second IC tag part is
IC chip,
A first antenna connected to the IC chip;
A second antenna disposed at a position facing the first antenna and electrically connected to a ground plate constituting the patch antenna;
The polarization-free IC tag according to claim 1. At least the first antenna and the second antenna are arranged at a predetermined interval from each other so as to enable electromagnetic inductive coupling,
The second antenna is a loop coil, and one end of the second antenna corresponding to the first IC tag portion is connected to a ground plate, and the other end is formed on a dielectric substrate stacked on the ground plate. Connected to the first feeding point through the first through hole,
One end of a second antenna corresponding to the second IC tag portion is connected to the ground plate, and the other end passes through a second through hole formed in the dielectric substrate and serves as the second feeding point. It is connected,
The polarization-free IC tag according to claim 7.

Images