JP5169329B2 - Planar antenna - Google Patents

Description

  The present invention relates to a planar antenna that can be suitably used as an IC tag antenna even when attached to a metal member.

  An IC tag composed of an antenna circuit and an IC circuit has features that are not available in barcodes, such as the ability to read multiple tags at once from a remote location using radio waves. Much attention has been paid to applications, and development and commercialization are progressing.

  Such an IC tag has a great influence on the communication characteristics due to the affixing member. In particular, when it is affixed to a metal member, the impedance matching between the affixed IC chip and the antenna is greatly deviated and received by the antenna. Power is not efficiently supplied to the IC chip. For this reason, the power required for driving the IC chip is insufficient, and communication becomes impossible.

  Therefore, there is a demand for a planar antenna for an IC tag that can supply power necessary for driving an IC chip even if it is attached to a metal member.

For such a planar antenna, the second antenna is formed on the first antenna formed on the first insulating material via the second insulating material, and the length of the second antenna is desired. An antenna capable of communicating even on a metal member by adjusting the length of the antenna is disclosed (Patent Document 1).
Japanese Patent Laying-Open No. 2005-210676

  However, in the configuration of the IC tag described in Patent Document 1, even when it is attached to a member other than metal, it is compared with the IC tag designed to be attached to a member other than metal due to the influence of the second antenna. As a result, the communication distance is considerably shortened.

  In view of the prior art as described above, the present invention enables communication even when pasted to a metal member without changing the design of the antenna using a planar antenna designed for pasting to a member other than metal. A planar antenna is provided.

In order to solve such a problem, the present invention has the following configuration. That is,
A first insulating substrate;
A dipole antenna with a T-shaped matching circuit on one surface side of the first insulating substrate;
A first loop circuit on the other surface side of the first insulating substrate;
When viewed from one surface of the first insulating substrate, the matching circuit portion of the projection image of the dipole antenna and the projection image of the first loop circuit intersect,
A second loop circuit is further provided on the other surface side of the first insulating substrate where the first loop circuit is present,
A second loop circuit is in contact with the first loop circuit ;
It is a planar antenna in which both end portions of the projected image of the dipole antenna and the projected image of the second loop circuit overlap when viewed from the one surface side where the dipole antenna of the first insulating substrate exists .

  According to the present invention, the impedance of the dipole antenna can be controlled by the first loop circuit without changing the shape of the dipole antenna. Therefore, even if the dipole antenna is designed for attachment other than a metal article, the dipole antenna can be used by being attached to the metal article simply by providing the first loop circuit.

  Hereinafter, embodiments of the present invention will be described in detail.

Flat surface antenna includes a first insulating substrate, one surface of the first insulating substrate (hereinafter referred to as surface A) and the T-shaped matching circuit with dipole antenna, the other surface of the first insulating substrate A first loop circuit on the side (hereinafter referred to as “B surface”), and a matching circuit portion of the projection image of the dipole antenna when viewed from one surface (A surface) of the first insulating substrate; It is characterized in that it intersects the projected image of the loop circuit.

As shown in FIG. 1, a dipole antenna with a T-shaped matching circuit is a T-shaped matching circuit connected to a dipole antenna in order to appropriately transfer power between a feeding point (IC chip in the case of an IC tag) and the antenna. Is an antenna with a configuration added. The dipole antenna of the present invention has two electrical conductors on the left and right sides, and a known dipole antenna such as a meander line can be used. The T-shaped matching circuit is a circuit provided to connect the two electric conductors of the dipole antenna. It is added for the purpose of impedance matching to properly transfer power between the feeding point and the antenna. Circuit.

As shown in FIGS. 1 and 3, the first loop circuit is a matching circuit portion of a projected image of a dipole antenna with a T-shaped matching circuit when viewed from one surface (A surface) of the first insulating substrate. And the projection image of the first loop circuit intersect each other. Accordingly, it is possible to change the impedance of the dipole antenna by changing only the shape of the first loop circuit without changing the design of the dipole antenna. The shape of the first loop circuit only needs to match the impedance. Preferably, if the shape is a square or a circle, a design simulation can be easily performed, and a quick design change can be performed.

  As shown in FIGS. 4 to 6, the planar antenna of the present invention further includes a second loop circuit on the other surface (B surface) side of the first insulating substrate, and the first loop circuit includes a second loop circuit. The loop circuit is in contact, and both ends of the projected image of the dipole antenna and the projected image of the second loop circuit overlap when viewed from one surface (A surface) of the first insulating substrate. It is preferable. By providing the second loop circuit in this way, it is possible to more precisely match the impedance matched in the first loop circuit. FIG. 7 shows a state where the first loop circuit and the second loop circuit are in contact with each other. In the present invention, the first loop circuit and the second loop circuit are in “contact” so that the line of one loop circuit is completely hidden behind the line of the other loop circuit as shown in FIG. And the state where two loop circuits partially overlap as shown in FIG. 7B, and the state where two loop circuits are in contact as shown in FIG. 7C are included. That is, the first loop circuit and the second loop circuit need only be in an electrically connected state. In FIGS. 6 and 7, the boundary line between the first loop circuit and the second loop circuit is illustrated for the sake of convenience, but the first loop circuit and the second loop circuit are actually shown in FIG. In many cases, the boundary is not formed clearly. The shape of the second loop circuit need only be able to match the impedance, and if it is preferably square or circular like the first loop circuit, the simulation of the design can be performed easily and the design can be changed quickly. It becomes possible.

  The projected image of the second loop circuit in the present invention only needs to overlap both end portions of the projected image of the dipole antenna, and the overlapping ratio may be adjusted as appropriate in accordance with the desired impedance matching.

  The dipole antenna with a T-shaped matching circuit, the first loop circuit, and the second loop circuit in the present invention are formed of an electric conductor. Examples of the electrical conductor include metals including at least one metal such as gold, silver, copper, aluminum, zinc, nickel, tin, and conductive polymers such as polyacetylene, polyparaphenylene, polyaniline, polythiophene, and polyparaphenylene vinylene. Metal particles such as gold, silver, copper, aluminum, platinum, iron, nickel, tin, zinc, solder, stainless steel, ITO, ferrite, etc., alloys and metal oxides, and conductive carbon (including graphite) Thermosetting resins mainly composed of polyester resin, phenoxy resin, epoxy resin, polyester resin, etc. containing conductive particles such as particles or resin particles plated with the particles, unsaturated polyester resins, polyester acrylate resins , Urethane acrylate resin, silicone acrylate resin Mainly containing an epoxy acrylate resin, it may be used known ones such as a conductive ink comprising a photocurable resin such as UV curable resin.

  In addition, as a method of forming a dipole antenna with a T-shaped matching circuit, a first loop circuit, and a second loop circuit, a metal foil, an etching method in which a metal vapor deposition layer is etched, a metal foil is cut out on a circuit board A known method such as a transfer method that is attached to the substrate or a printing method that is formed by printing using a conductive ink can be used.

  In the planar antenna of the present invention, as shown in FIGS. 8 and 9, it is preferable that a second insulating substrate is further laminated on the other surface (B surface) side of the first insulating substrate. By laminating the second insulating substrate, when the planar antenna of the present invention is attached to another article, the insulation between the first loop circuit and the second loop circuit and the attached article is maintained, and the circuit is Good function can be demonstrated.

  The first and second insulating substrates in the present invention may be substrates that can ensure electrical insulation of the dipole antenna with a T-shaped matching circuit, the first loop circuit, and the attached article. Preferably, a resin film is preferable in terms of price and weight. A resin film is a melt extrusion molding of polyester, foamable polyester, polyolefin, polylactic acid, polyamide, polyesteramide, polyether, polystyrene, polyphenylene sulfide, polyetherester, polyvinyl chloride, poly (meth) acrylic acid ester, etc. A film obtained by processing a possible material, and may be any of an unstretched film, a uniaxially stretched film, and a biaxially stretched film. Among these, a polyester film, a polyolefin film, and a polyphenylene sulfide film are preferable from the viewpoint of price and mechanical characteristics, and a biaxially stretched polyester film is particularly preferable because of excellent balance of price, heat resistance, and mechanical characteristics.

  Further, it is preferable that the second insulating substrate includes a radio wave absorber because even if the attached article is a metal, the influence of the metal article on the dipole antenna becomes smaller, and therefore, good communication characteristics can be maintained. The configuration in which the second insulating substrate includes a radio wave absorber includes a case where the entire second insulating substrate is a radio wave absorber, and a case where the second insulating substrate is a laminated body including a layer of the radio wave absorber. As the radio wave absorber, a magnetic material made of at least one of soft magnetic material, soft magnetic metal oxide, magnetic metal and magnetic metal oxide is mixed with a binder such as resin, TPE, rubber and the like. Known materials such as sheets and films can be used.

  The thickness of the first insulating substrate in the present invention is preferably 1 to 250 μm, more preferably 10 to 125 μm, and still more preferably 20 to 75 μm, from the viewpoints of flexibility and mechanical strength. Further, the thickness of the second insulating substrate in the present invention is preferably 0.05 to 3 mm, more preferably 0.5 to 2 mm, from the viewpoint of suppressing the influence of the attached article and reducing the thickness.

Hereinafter, the present invention will be described with reference to examples. The evaluation method of the sample created in each example, comparative example, and reference example is shown below.
[Evaluation method]
1. Communication distance of IC tag The sample is in the state of an IC tag mounted with an IC chip, and the communication distance is measured at 950 MHz.
As a measuring instrument, an Omron reader / writer (model: V750-BA50CO4-JP) and an Omron antenna (model: V750-HS01CA-JP) were used. In a 3 m method anechoic chamber, the antenna is fixed at a position 90 cm from the floor, the IC tag is positioned so that it faces the same height, and the reader / writer measures the distance by moving the IC tag back and forth. The communication distance is the distance at which communication between the IC tag and the IC tag can be read without error.

2. The thickness of each member The sample was cut | disconnected in the thickness direction with the microtome, this cross section was observed using SEM of 10,000 times, and the thickness of each member was measured. The measurement was performed with one sample for each item, and 5 points per field per sample were measured. The average value was defined as the thickness of each member in the present invention.

( Reference Example 1)
An aluminum layer having a thickness of 0.001 mm is formed on one surface of a biaxially stretched polyethylene terephthalate film having a thickness of 0.075 mm (Lumirror S10, manufactured by Toray Industries, Inc.) using an electron beam (EB) vapor deposition method. A film was obtained. The obtained metallized film was etched by wet etching so that a = 53 mm, b = 21 mm, c = 47 mm, and d = 7 mm in FIG. 3 to form a first loop circuit. An UHF tag (ALN-9540-Squiggle) manufactured by Alien, in which a dipole antenna with a T-shaped matching circuit was formed on a first insulating substrate, was prepared. The face of the biaxially stretched polyethylene terephthalate film on which the first loop circuit is formed faces the face of the UHF tag where the dipole antenna is not formed, so that the matching circuit portion of the projected image of the dipole antenna and the first loop circuit It was pasted so as to intersect the projected image. Next, a 1.0 mm-thick wave absorber (NEC TOKIN Corporation Busterade Model: EFR) was attached to the surface of the biaxially stretched polyethylene terephthalate film where the first loop circuit was not formed. A laminate of this biaxially stretched polyethylene terephthalate and a radio wave absorber was used as the second insulating substrate. And an IC tag using a flat surface antenna in this manner.

  When the IC tag was attached to a metal foil and the communication distance was measured, the communication distance was 600 mm. Further, the thickness of the planar antenna was 1.2 mm, which was sufficiently thin as an IC tag that can be attached to metal.

(Example 1 )
An aluminum layer having a thickness of 0.001 mm is formed on one surface of a biaxially stretched polyethylene terephthalate film having a thickness of 0.075 mm (Lumirror S10, manufactured by Toray Industries, Inc.) using an electron beam (EB) vapor deposition method. A film was obtained. The obtained metallized film was subjected to wet etching. In FIG. 6, the first loop circuit was the same as in Reference Example 1, and the second loop circuit was e = 53 mm, f = 96 mm, g = 47 mm, h = 31 mm. Etching was performed to form the first and second loop circuits. A UHF tag (ALN-9540-Squiggle) manufactured by Alien, in which a dipole antenna with a T-shaped matching circuit was formed on a first insulating substrate, was prepared. The surface of the biaxially stretched polyethylene terephthalate film on which the first and second loop circuits are formed faces the surface on which the dipole antenna of the UHF tag is not formed, and the matching circuit portion of the projected image of the dipole antenna and the first Affixed so that the projected image of the loop circuit intersected. At that time, the both ends of the projected image of the dipole antenna were pasted so as to be completely hidden by the both ends of the projected image of the second loop antenna. Thereafter, a 1.0 mm-thick wave absorber (NEC Tokin Co., Ltd. Busterade Model: EFR) was attached to the surface of the biaxially stretched polyethylene terephthalate film where the first and second loop circuits were not formed. A laminate of this biaxially stretched polyethylene terephthalate and a radio wave absorber was used as the second insulating substrate. In this way, an IC tag using the planar antenna of the present invention was obtained.

  When the IC tag was attached to a metal foil and the communication distance was measured, the communication distance was 420 mm. Further, the thickness of the planar antenna was 1.2 mm, which was sufficiently thin as an IC tag that can be attached to metal.

(Comparative Example 1)
When an UHF tag (ALN-9540-Squiggle) manufactured by Alien was attached to a metal foil and the communication distance was measured, communication was not performed.

(Comparative Example 2)
The UHF tag (ALN-9540-Squiggle) manufactured by Alien is attached to one side of a 1.0 mm-thick wave absorber (NEC TOKIN Co., Ltd. Busterade model: EFR). When we measured the communication distance with the foil attached, we did not communicate.

  If the planar antenna of the present invention is used, even if the IC tag is designed to be pasted other than a metal article, it can be used as an IC tag that can be used by being affixed to a metal article.

It is a schematic plan view of a dipole antenna surface of the flat surface antenna. FIG. 2 is a schematic cross-sectional view taken along the line II of the planar antenna illustrated in FIG. 1. FIG. 2 is a schematic plan view of a first loop circuit surface of the planar antenna shown in FIG. 1. It is a schematic plan view of the dipole antenna surface of the planar antenna of one embodiment in the present invention. FIG. 5 is a schematic cross-sectional view taken along the line II of the planar antenna illustrated in FIG. 4. FIG. 5 is a schematic plan view of a first loop circuit surface and a second loop circuit surface of the planar antenna shown in FIG. 4. It is a figure which shows the contact state of a 1st loop circuit and a 2nd loop circuit. FIG. 2 is a schematic cross-sectional view taken along the line II when a second insulating substrate is stacked on the first loop circuit of the planar antenna shown in FIG. 1. FIG. 5 is a schematic cross-sectional view taken along the line II when a second insulating substrate is stacked on the first loop circuit and the second loop circuit of the planar antenna illustrated in FIG. 4.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Dipole antenna 2 1st insulating substrate 3 T-shaped matching circuit 4 1st loop circuit 5 2nd loop circuit 6 2nd insulating substrate

Claims (5)

A first insulating substrate;
A dipole antenna with a T-shaped matching circuit on one surface side of the first insulating substrate;
A first loop circuit on the other surface side of the first insulating substrate;
When viewed from one side of the first insulating substrate, the matching circuit portion of the projection image of the dipole antenna and the projection image of the first loop circuit intersect ,
A second loop circuit is further provided on the other surface side of the first insulating substrate where the first loop circuit is present,
A second loop circuit is in contact with the first loop circuit;
A planar antenna in which both end portions of the projected image of the dipole antenna and the projected image of the second loop circuit overlap each other when viewed from one surface side where the dipole antenna of the first insulating substrate exists . The planar antenna according to claim 1, wherein the first loop circuit is square or circular. The planar antenna according to claim 1 or 2 , wherein the second loop circuit is square or circular. The planar antenna according to any one of claims 1 to 3, wherein a second insulating substrate is further laminated on the other surface side of the first insulating substrate where the first loop circuit exists. The planar antenna according to claim 4 , wherein the second insulating substrate includes a radio wave absorber.

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