JP2009182446A - Antenna - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an antenna which has a performance equal to or higher than that of a conventional antenna, in which a feeding part and a radiating element are integrally formed, and also reduce manufacturing cost and facilitate specification change. <P>SOLUTION: A compact loop circuit provided with a feeding part and a radiating element which is excited by a high frequency magnetic field to be able to radiate an electric wave are formed separately from each other. The compact loop circuit and the radiating element are disposed so as to be laminated in a direction orthogonal to a plane wherein the compact loop circuit is located, while magnetic coupling with each other so that at least a part of the compact loop circuit overlaps the radiating element when viewed in the direction orthogonal to the plane. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an antenna such as a dipole antenna.

  An antenna such as a dipole antenna can accurately and efficiently transmit and receive identification information in cooperation with a transmitting and receiving element such as an IC chip, so that it can be used in various fields such as logistics management and human entry / exit management. It's being used.

  The dipole antenna includes a power feeding unit having a pair of power feeding points respectively connected to a pair of connection terminals in the transmitting / receiving element, and a radiating element extending from the power feeding unit to one side and the other side.

  The conventional dipole antenna has a problem that it is difficult to reduce the manufacturing cost and to cope with the specification change because the feeding portion and the radiating element are integrally formed (see FIG. 6 below).

That is, strict dimensional accuracy is required for manufacturing the power feeding unit.
Therefore, in the conventional antenna in which the feeding unit and the radiating element are integrally formed, the entire antenna is manufactured by a manufacturing method (for example, etching process) that satisfies the dimensional accuracy required for the feeding unit. There is a problem that the manufacturing cost is high.
Furthermore, when the specification is changed in the conventional configuration, it is necessary to remanufacture the entire antenna including the power feeding unit and the radiating element.

  The present invention has been made in view of the prior art, and has an antenna performance equal to or higher than that of a conventional antenna in which a feeding portion and a radiating element are integrally formed, while reducing manufacturing costs and easily changing specifications. An object of the present invention is to provide an antenna that can be simplified.

  In order to achieve the above-described object, the present invention provides a conductor having a substantially annular shape in the same plane so that one end portion and the other end portion are respectively connected to a pair of connection terminals in a transmitting / receiving element. A small loop circuit that generates a high-frequency magnetic field and a radiating element that is excited by the high-frequency magnetic field and can radiate radio waves, the radiating element formed separately from the small loop circuit, At least a part of the small loop circuit overlaps the radiating element when viewed in a direction orthogonal to a plane on which the small loop circuit is located in a state where the loop circuit and the radiating element are magnetically coupled. Thus, an antenna is provided that is stacked in the orthogonal direction.

The small loop circuit has a straight side extending linearly over a predetermined distance, and the radiating element is linear over a predetermined distance to one end side and the other end side with respect to a central position in the longitudinal center. May have a straight portion extending to
In such a configuration, preferably, the small loop circuit and the radiating element are stacked in the orthogonal direction so that the linear side and the linear portion overlap each other in the orthogonal direction when viewed in the orthogonal direction. Is done.

More preferably, the central position of the straight side is located at the same position as the central position with respect to the longitudinal position of the radiating element.
More preferably, the straight side and the straight part have the same width, and the straight side and the straight part are located at the same position with respect to the width direction position of the radiation element.

  In the various configurations, the small loop circuit is preferably laminated on a dielectric base film to form a small loop circuit unit, and the small loop circuit unit is fixed to the radiating element.

  According to the antenna of the present invention, when the small loop circuit and the radiating element formed separately from each other are magnetically coupled, the antenna is viewed in a direction perpendicular to the plane on which the small loop circuit is located. Since at least a part of the small loop circuit is stacked in the orthogonal direction so as to overlap the radiating element, the antenna performance is equal to or better than that of the conventional antenna in which the feeding portion and the radiating element are integrally formed. In addition, the manufacturing cost can be reduced and the specification can be easily changed.

Hereinafter, preferred embodiments of an antenna according to the present invention will be described with reference to the accompanying drawings.
FIG. 1 shows a perspective view of an antenna 1A according to the present embodiment.
2A and 2B are a plan view and a front view of the antenna 1A, respectively.
Further, FIG. 3 shows a partially enlarged front view of the antenna 1A.

The antenna 1A forms an RFID inlet that transmits and / or receives signals in cooperation with a transmitting / receiving element 100 such as an IC chip.
Specifically, the antenna 1A includes a small loop circuit 11 that generates a high-frequency magnetic field in cooperation with the transmission / reception element 100, and a radiating element 21 that can be excited by the high-frequency magnetic field to emit radio waves.

The small loop circuit 11 is formed of a conductor that is substantially annular in the same plane so as to form feeding points 12a and 12b whose one end and the other end are connected to a pair of connection terminals in the transmitting / receiving element. A high frequency magnetic field is generated in cooperation with the transmitting / receiving element 100.
For example, the small loop circuit 11 is formed so that the electrical length is less than ½ of the signal wavelength.

The electrical length of the radiating element 21 is appropriately set so that it can be excited by a high-frequency magnetic field and radiate a radio wave having a gain according to specifications.
The electrical length of the radiating element 21 is, for example, an integral multiple of ½ of the signal wavelength, or a length slightly shorter than ½ of the signal wavelength (such as 40% of the signal wavelength).

  In the present embodiment, as shown in FIGS. 1 to 3, the small loop circuit 11 and the radiating element 21 are formed separately, and the small loop circuit 11 is magnetically coupled to each other. When viewed in a direction orthogonal to the plane on which the loop circuit 11 is located (in plan view), at least a part of the small loop circuit 11 is stacked in the orthogonal direction so as to overlap the radiation element 21. ing.

  According to the antenna 1A having such a configuration, the manufacturing cost can be reduced as compared with a conventional antenna in which a feeding portion including a feeding point and a radiating element are integrally formed.

That is, strict dimensional accuracy is required for the slit 13 between the pair of feeding points 12a and 12b connected to the pair of connection terminals in the transmitting / receiving element 100 and the width of the conductor forming the feeding unit. In particular, when the matching circuit is formed by the shape and arrangement of the conductors constituting the power feeding unit, more strict dimensional accuracy is required.
On the other hand, the radiating element 21 is not required to have such strict dimensional accuracy as long as the radiating characteristics according to the specifications are exhibited.

However, in the conventional configuration in which the feeding portion including the feeding point and the radiating element are integrally formed, the entire antenna including the feeding portion and the radiating element is manufactured by a manufacturing method that satisfies the dimensional accuracy required for the feeding portion. Need to manufacture.
In general, an etching process is exemplified as a manufacturing method that satisfies strict dimensional accuracy. However, when the feeding portion and the radiating element are integrally formed by this etching process, a large area is required for an expensive material. And precise etching, which increases costs. Furthermore, when the entire antenna including the power feeding unit and the radiating element is etched, it is difficult to efficiently remove the material from the base material, which easily causes a material loss. Invite.

On the other hand, in the antenna 1A according to the present embodiment, as described above, the small loop circuit 11 having the feeding points 12a and 12b and the radiating element 21 are separately formed.
According to such a configuration, only the small loop circuit 11 having a small area is manufactured by a manufacturing method that satisfies strict dimensional accuracy (for example, etching using an aluminum foil), and the radiation element 21 having a large area is used. Is an inferior dimensional accuracy but inexpensive manufacturing method (for example, a method of printing conductive ink on resin or paper, or a method of printing conductive ink on a package of an object to which the antenna 1A is to be fixed) Alternatively, it can be manufactured by a method of attaching a metal stay to the package).

  Accordingly, it is possible to reduce the cost as compared with the conventional configuration in which the entire antenna including the feeding portion and the radiating element must be formed by a manufacturing method that can satisfy strict dimensional accuracy such as etching. .

In order to improve the efficiency of connecting the transmitting / receiving element 100 to the feeding points 12a and 12b of the small loop circuit 11, the planarity of the feeding points 12a and 12b is important.
Considering this point, preferably, as shown in FIGS. 1 to 3, the small loop circuit 11 is laminated on a base film 15 made of a dielectric material such as a resin to form a small loop circuit unit 10. Can be configured.
According to such a configuration, it is possible to effectively prevent warping or the like from being deformed in the small loop circuit 11 when the small loop circuit 11 is formed, and the work efficiency of connecting the transmitting / receiving element 100 to the feeding points 12a and 12b. Can be improved.

  The small loop circuit unit 10 includes, for example, a step of laminating a conductor such as aluminum or copper forming the small loop circuit 11 on the base film 15, and a laminated body composed of the base film 15 and the conductor. It is easily manufactured by a manufacturing method including a step of forming the small loop circuit 11 from the conductor by etching.

  In the present embodiment, as shown in FIGS. 1 to 3, the radiating element 21 is also laminated on a base film 25 made of a dielectric material such as a resin, and the radiating element unit 20 is formed together with the base film 25. is doing.

  For example, the radiating element unit 20 includes a step of preparing the base film 25 and a step of forming the radiating element 21 by printing a conductive ink on the base film 25 in a predetermined shape. Easy to manufacture.

The small loop circuit 11 and the radiating element 21 can be coupled by, for example, an adhesive or ultrasonic waves.
Further, as in the present embodiment, when the small loop circuit 11 is laminated on the base film 15, the small loop circuit 11 is made to be the radiating element by thermally fusing the base film 15. It is also possible to fix to 21.

The present embodiment in which the small loop circuit 11 and the radiating element 21 are separately formed has an effect that it is possible to easily cope with a change in antenna specifications in addition to a reduction in manufacturing cost.
That is, in the conventional configuration in which the feeding unit and the radiating element are integrally formed, in order to obtain an antenna having different specifications, it is necessary to remanufacture the entire antenna including the feeding unit and the radiating element.
On the other hand, in the present embodiment, for example, antennas having different specifications can be obtained by using only the small loop circuit 11 as a common component and changing only the radiating element 21.

Preferably, the small loop circuit 11 overlaps the radiating element 21 over approximately ½ or more of the circumference.
By providing such a configuration, the radiation characteristics of the antenna can be improved.

FIG. 2 (c) shows a plan view of the radiating element 21 in the antenna 1A.
In order to facilitate manufacture while improving antenna radiation characteristics, the small loop circuit 11 is provided with a straight side 110 (see FIGS. 1 and 2A) extending linearly over a predetermined distance, and The radiating element 21 is provided with a straight line portion 210 extending linearly over a predetermined distance to one end side and the other end side with respect to the central position C in the center in the longitudinal direction (see FIG. 2 (c)). The small loop circuit 11 and the radiating element 21 can be stacked in the orthogonal direction so that 110 and the linear portion 210 overlap each other when viewed in the orthogonal direction while being parallel to each other.

In the present embodiment, the small loop circuit 11 has a substantially rectangular shape in plan view, as shown in FIGS.
Specifically, the small loop circuit 11 has one end portion forming one side 12a of the pair of feeding points, and one end portion forming the other 12b of the pair of first feeding points, the slit 13 A second power supply side 111b disposed opposite to the first power supply side 111a and extending to the opposite side of the first power supply side 111a, and one end of the other end of the first and second power supply sides 111a, 111b And first and second short sides 112a and 112b extending in parallel to each other in directions orthogonal to the first and second feeding sides 111a and 111b, respectively, and the first and second sides A long side 113 connecting the other ends of the first and second short sides 112a and 112b so as to extend in parallel with the power feeding sides 111a and 111b.
In such a configuration, the long side 113 forms the straight side 110.

More preferably, as shown in FIG. 2, the longitudinal center position of the straight side 110 is located at the same position as the center position C with respect to the longitudinal position of the radiation element 21.
With this configuration, the antenna 1A can be used as a dipole antenna having excellent radiation characteristics.

More preferably, as shown in FIG. 2, the straight side 110 and the straight part 210 have the same width, and the straight side 110 and the straight part 210 are located at the same position with respect to the position in the width direction of the radiation element 21. Can be made.
According to such a configuration, the antenna characteristics can be further improved.

In the present embodiment, as shown in FIG. 2 (c), the radiating element 21 is entirely linear including the straight portion 210, but has a shape as shown in FIG. It is also possible.
That is, the radiating element 21 </ b> A shown in FIG. 4A has wide capacitor regions 215 on both sides of the linear portion 210. According to such a configuration, the longitudinal length of the entire antenna can be shortened.
The radiation element 21B shown in FIG. 4B includes a first radiation region 221 extending straight from the straight portion 210, and second and third radiations bent from the first radiation region 221 via an inflection point. Regions 222 and 223. According to such a configuration, the bandwidth of the resonance frequency can be widened.
The radiation elements 21C and 21D shown in FIG. 4C and FIG. 4D have bending regions 230C and 230D that are bent through a plurality of inflection points between the linear portion 210 and both ends. Yes. According to such a configuration, the longitudinal length of the entire antenna can be shortened.

Here, an analysis result obtained by using the finite element method for the antenna characteristic (S11 characteristic) of an example (hereinafter referred to as an example) of the antenna 1A according to the present embodiment will be described.
FIGS. 5A and 5B are a plan view and a side view of the antenna 50 according to the embodiment, respectively.
In the embodiment, the small loop circuit 11 and the radiating element 21 are made of aluminum, and the base film 15 in the small loop circuit unit 10 is made of polyethylene (relative dielectric constant εr = 3.2).
The dimensions of each member are as shown in FIGS. 5 (a) and 5 (b).

The same analysis was performed on an example of a conventional dipole antenna (hereinafter referred to as a comparative example) in which the feeding unit and the radiating element are integrally formed.
FIGS. 6A and 6B are a plan view and a side view of the antenna 900 according to the comparative example, respectively.
In the comparative example, the feeding part 910 and the radiating element 920 including the feeding point are formed of aluminum.
The dimensions of each member are as shown in FIGS. 6 (a) and 6 (b).

In FIG. 7, the analysis result of the said Example and the said comparative example is shown.
As shown in FIG. 7, in both the example and the comparative example, the S11 value is significantly below −10 dB, which is a practical level index, and both have sufficient antenna characteristics.
Therefore, it was confirmed that the example has antenna characteristics equal to or higher than those of the comparative example while reducing the cost and facilitating specification change.

FIG. 1 is a perspective view of an antenna according to an embodiment of the present invention. 2A and 2B are a plan view and a front view of the antenna shown in FIG. 1, respectively. FIG. 2 (c) is a plan view of a radiating element in the antenna. FIG. 3 is a partially enlarged front view of the antenna shown in FIGS. 1 and 2. 4 (a) to 4 (d) are plan views of an antenna according to a modification of the present invention. 5A and 5B are a plan view and a side view, respectively, of an example (example) of the antenna according to the present invention. FIGS. 6A and 6B are a plan view and a side view of an example (comparative example) of a conventional dipole antenna, respectively. FIG. 7 is a graph showing the results of analysis relating to the S11 characteristic in the example and the comparative example using the finite element method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1A Antenna 10 Small loop circuit unit 11 Small loop circuit 12a, 12b Feeding point 15 Base film 21 Radiating element 110 Straight line 210 of small loop circuit Straight line part C of a radiating element Longitudinal center position of a radiating element

Claims (5)

A small loop circuit for generating a high-frequency magnetic field, which is formed by a conductor that is substantially annular in the same plane so as to form a feeding point that is connected to a pair of connection terminals in a transmitting / receiving element at one end and the other end, A radiating element that is excited by a high-frequency magnetic field and can radiate radio waves, comprising a radiating element formed separately from the small loop circuit,
When the small loop circuit and the radiating element are magnetically coupled and viewed in a direction perpendicular to a plane on which the small loop circuit is located, at least a part of the small loop circuit overlies the radiating element. An antenna, wherein the antennas are stacked in the orthogonal direction so as to wrap. The small loop circuit has a straight side extending linearly over a predetermined distance,
The radiating element has a linear portion extending linearly over a predetermined distance to one end side and the other end side with respect to the center position in the longitudinal center,
2. The antenna according to claim 1, wherein the small loop circuit and the radiating element are overlapped when viewed in the orthogonal direction in a state in which the straight side and the straight portion are parallel to each other.   The antenna according to claim 2, wherein a central position of the straight side is located at the same position as the central position with respect to a longitudinal position of the radiating element. The straight side and the straight portion have the same width,
4. The antenna according to claim 2, wherein the straight side and the straight part are located at the same position with respect to a position in the width direction of the radiating element. 5. The small loop circuit is laminated on a base film made of a dielectric to form a small loop circuit unit,
The antenna according to any one of claims 1 to 4, wherein the small loop circuit unit is fixed to the radiating element.

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