JP2014146947A - Antenna element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an antenna element in which deterioration of antenna characteristics is reduced in the reactance adjustment, even if using conductors having a small wire size, e.g., a single wire or a Litz wire.SOLUTION: An antenna element comprises: a first electrode plate 3 for connection with one end of a loop coil 1; a second electrode plate 4 for connection with the other end of the loop coil 1; an insulating substrate 5; and a conductive plate. The conductive plate comprises: a fixed capacity conductive plate 8 overlapping the projection plane of the first electrode plate 3 in the thickness direction at least partially; a plurality of adjustment conductive plate 9 overlapping the projection plane of the second electrode plate 4 in the thickness direction at least partially; and a wiring part 10 for connecting each adjustment conductive plate 9 with the fixed capacity conductive plate 8. Reactance of the antenna element is adjusted by changing the quantity, i.e., the area of the adjustment conductive plates 9 for connection with the fixed capacity conductive plate 8, thereby changing the capacity component generated between the first and second electrode plates 3, 4 of the loop coil 1.

Description

  The present invention relates to a radio communication system such as an RFID system, and an antenna element used for non-contact power feeding.

  In an RFID system or the like, when performing wireless communication between a non-contact IC card or IC tag and an RFID reader / writer, the reactance is adjusted by the capacity component or inductive component of the antenna element used in order to obtain desired communication characteristics. Thus, the frequency characteristics of the antenna element are adjusted.

  Patent Document 1 discloses a planar antenna element having a parallel resonance pattern that capacitively couples an inner periphery and an outer periphery of an antenna pattern in a planar antenna element having a spiral planar antenna pattern, The frequency component of the antenna element can be adjusted by changing the capacitance component by changing the number and area of the parallel resonance patterns.

JP 2009-239487 A

  Since the antenna element of Patent Document 1 generates a capacitive component between the antenna pattern and the parallel resonance pattern, the antenna pattern needs to have a width corresponding to the desired capacitive component. By the way, as an antenna element used for an RFID tag or the like, an antenna element in which a litz wire or the like obtained by twisting a single wire or a plurality of fine wires is wound in a loop coil shape is also used depending on the application.

  When a conductor having a small diameter such as a single wire or a litz wire is used for the antenna element, the capacitance component between the antenna pattern and the conductor plate acting as a parallel resonance pattern is small. Therefore, in order to obtain a sufficient capacitance component to adjust the reactance of the antenna element, it is necessary to increase the area of the conductor plate. However, if a conductor plate having a large area is arranged close to the antenna pattern in this way, There is a problem that the antenna characteristic is deteriorated due to an increase in the resistance value of the antenna element.

  The present invention has been made in order to solve the above-described problems in the prior art, and an object of the present invention is to perform reactance adjustment with less deterioration of antenna characteristics in an antenna element using a conductor having a small diameter such as a single wire or a litz wire. An antenna element that can be used is provided.

  To achieve the above object, an antenna element of the present invention is connected to a loop coil, a first electrode plate connected to one end of the loop coil, and the other end of the loop coil. A second electrode plate, an insulating substrate, and a conductive plate, wherein the first electrode plate and the second electrode plate are disposed on one surface of the insulating substrate; The projection surface in the thickness direction of the first electrode plate and the second electrode plate is disposed on the other surface of the conductive substrate and overlaps at least part of the projection surface in the thickness direction of the conductive plate. It is characterized by.

  The conductive plate of the antenna element of the present invention includes a constant-capacity conductive plate that overlaps at least a part of a projection surface in the thickness direction with the first electrode plate, and a projection in the thickness direction with the second electrode plate. It is characterized by comprising a plurality of adjustment conductive plates at least partially overlapping the surface and a wiring part for connecting the adjustment conductive plate to the constant capacity conductive plate.

  Furthermore, the antenna element manufacturing method of the present invention is characterized in that at least a part of the wiring section is cut so that the reactance of the antenna element matches a preset value.

  In the antenna element of the present invention, an electrode plate is connected to both ends of a loop coil, and a conductive plate is disposed with an insulating substrate interposed therebetween so as to face the electrode plate. Capacitance components can be generated in between. For this reason, there is no need to create a capacitive component by making the loop coil conductor and the conductive plate face each other. Capacitance components can be easily obtained.

  In addition, since the antenna pattern of the loop coil is not used for generating the capacitance component, and the conductive plate is not close to the antenna pattern, the antenna characteristics change due to electromagnetic coupling between the loop coil conductor and the conductive plate. Can be suppressed. Thereby, in reactance adjustment, an antenna element with reduced deterioration of antenna characteristics can be obtained.

  Further, in the antenna element of the present invention, a capacitive component can be obtained between both ends of the loop coil as described above, but the electromotive voltage generated in the loop coil is maximized between both ends of the loop coil. If the dielectric constant and thickness of the insulating substrate are the same, the area of the electrode plate and the conductive plate necessary to obtain the same capacitance component can be minimized, and the electromagnetic influence on the loop coil conductor can be further reduced. It is possible to reduce.

  Furthermore, in the antenna element of the present invention, a conductive plate facing one of the electrode plates connected to both ends of the loop coil is used as a plurality of adjustment conductive plates, and this adjustment conductive plate is opposed to the other electrode plate using wiring. Connect to a constant capacity conductive plate. By changing the number or area of the adjustment conductive plates, the area of the conductive plate that generates the capacitive component can be changed. Accordingly, the capacitance component added to the antenna element can be easily changed, so that the area of the conductive plate can be adjusted so as to obtain a required capacitance component according to the use of the antenna element.

  In addition, the conductive plate facing the electrode plate across the insulating layer is not directly connected to the loop coil conductor or the electrode plate, and the area of the conductive plate can be changed by changing the number of adjusting conductive plates. Therefore, the electrode plate and the loop coil conductor need not be changed in shape. Therefore, since the capacitive component and the inductive component of the electrode plate itself or the loop coil itself are not changed, the influence on the antenna characteristics can be limited to only the capacitive component added by the conductive plate. For this reason, there is an advantage that the design of the antenna element becomes easy.

  Furthermore, the antenna element of the present invention can change the quantity of the adjustment conductive plate connected to the constant capacity conductive plate by cutting a part of the wiring portion, and can change the area for generating the capacitive component of the conductive plate. it can. Thus, even after the process of attaching the conductive plate to the insulating substrate, the area of the conductive plate is changed so that the reactance of the antenna element matches the preset value, and the reactance of the antenna element is adjusted. Is possible.

  In the present invention, the fact that the reactance of the antenna element coincides with a preset value means that the reactance value and its allowable value are determined in advance, and the reactance of the antenna element is within this allowable value range. The reactance value and the allowable value are determined according to the use of the antenna element.

  As described above, according to the present invention, it is possible to provide an antenna element capable of performing reactance adjustment with little deterioration in antenna characteristics even in an antenna element using a conductor having a small diameter such as a single wire or a litz wire.

1A and 1B are diagrams illustrating a configuration of an antenna element according to a first embodiment of the present invention, in which FIG. 1A is a plan view and FIG. 1B is a cross-sectional view taken along line AA in FIG. It is a figure which shows the structure of the antenna element by the 2nd Embodiment of this invention, Fig.2 (a) shows a top view, FIG.2 (b) shows a bottom view. It is a top view which shows the structure of the antenna element by a prior art. It is a figure which shows the relationship between the total area of an adjustment electrically conductive board, and a reactance change rate about the Example and comparative example of this invention. It is a figure which shows the relationship between the total area of an adjustment electrically conductive board, and antenna resistance value about the Example and comparative example of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
1A and 1B are diagrams showing a configuration of an antenna element according to a first embodiment of the present invention. FIG. 1A is a plan view, and FIG. 1B is a cross-sectional view taken along line AA in FIG. Show.

  As shown in FIG. 1, the antenna element of the present invention includes a loop coil 1 and a terminal portion 2, and the terminal portion 2 includes a first electrode plate 3 connected to one end of the loop coil 1, and a loop. A second electrode plate 4 connected to the other end of the coil 1, an insulating substrate 5, and a conductive plate 6 are provided. Further, as shown in FIG. 1, a substrate 7 may be disposed to support the loop coil 1. The first electrode plate 3 and the second electrode plate 4 are disposed on one surface of the insulating substrate 5, and the conductive plate 6 is disposed on the other surface of the insulating substrate 5 with the first electrode plate 3 and The second electrode plate 4 is disposed so as to at least partly overlap with the projection surface in the thickness direction of the second electrode plate 4, the overlapping portion of the first electrode plate 3 and the conductive plate 6, and the second electrode plate 4 and the conductive plate 6. Capacitance components can be obtained with overlapping portions.

  The loop coil 1 can be used by using a conductive wire having an insulation coating such as an enameled wire as a single wire or a stranded wire such as a litz wire. Moreover, you may produce using a printed circuit board or a flexible printed circuit board. The cross section of the conducting wire is not limited to a circular shape, and may be a polygonal shape. The shape of the loop coil 1 may be a polygonal shape or a circular shape in addition to the quadrangular shape as shown in FIG. Further, the arrangement of the loop coil 1 is not limited to one plane, and may be arranged along a plurality of intersecting planes. In FIG. 1, the number of turns of the loop coil is three, but the number of turns is not limited to this, and it may be applied to a loop coil having one turn.

  Although the terminal part 2 may be produced using a double-sided printed board, the first electrode plate 3, the second electrode board 4 and the insulating board 5 are produced using a single-sided printed board. A conductive foil such as aluminum foil or copper foil may be attached to the insulating substrate 5 with a double-sided adhesive tape or the like. In this case, the size and bonding position of the conductive foil can be changed. It becomes easy to change. Further, the arrangement of the terminal portion 2 is not limited to the inside of the loop coil 1 and may be arranged outside the loop coil 1. The first electrode plate 3 and the second electrode plate 4 may use conductor pads for connecting an antenna to a circuit board such as a non-contact IC card or an RFID tag. What is necessary is just to select the material and thickness of the insulating substrate 5 which can obtain the capacity | capacitance component required according to a use.

  When the loop coil 1 is manufactured using a printed circuit board or a flexible printed circuit board, the dielectric layer of the printed circuit board or the flexible printed circuit board is the substrate 7, and the substrate 7 and the insulating substrate 5 of the terminal portion 2 are integrated. Also good.

  A soft magnetic sheet may be used for the substrate 7 depending on the application. As the soft magnetic sheet, a soft magnetic ferrite sheet, a soft magnetic alloy powder mixed with an organic binder such as a resin binder and formed into a sheet can be used.

(Second Embodiment)
2A and 2B are diagrams showing a configuration of an antenna element according to the second embodiment of the present invention, in which FIG. 2A is a plan view and FIG. 2B is a bottom view.

  In the second embodiment of the antenna element of the present invention, as shown in FIG. 2B, the conductive plate is a constant-capacity conductive plate in which at least a part of the projection surface in the thickness direction overlaps the first electrode plate 3. 8, a plurality of adjustment conductive plates 9 that overlap at least a part of the projection surface in the thickness direction with the second electrode plate 4, and a wiring portion 10 that connects each of the adjustment conductive plates 9 to the constant capacitance conductive plate 8. ing. The other points are the same as those of the first embodiment shown in FIG.

  The adjustment conductive plates 9 need not be arranged in one row as shown in FIG. 2B, but may be arranged in a plurality of rows. In FIG. 2B, the number of the adjustment conductive plates 9 is three, but is not limited to this. Further, the adjustment conductive plates may be connected by wiring, and a plurality of adjustment conductive plates may be connected to the constant capacity conductive plate 8 by wiring as one group. The shapes of the adjustment conductive plates 9 do not have to be the same, and may have different sizes or different shapes.

  The antenna element of the present invention can change the quantity, that is, the area of the adjustment conductive plate 9 connected to the constant capacity conductive plate 8 by cutting a part of the wiring portion 10. For example, when the portion of the wiring portion 10 that connects between the adjustment conductive plate 91 and the adjustment conductive plate 92 is deleted, the adjustment conductive plate 91 can be disconnected from the constant capacitance conductive plate 8 and connected to the constant capacitance conductive plate 8. The quantity, that is, the area of the adjusting conductive plate 9 to be adjusted can be changed. As a result, the capacitance component generated between the first electrode plate 3 and the second electrode plate 4 connected to both ends of the loop coil 1 is changed, so that the reactance of the antenna element matches the preset value. Can be adjusted.

(Example)
As an example of the present invention, the configuration shown in FIG. 2 was used. The loop coil 1 was made of a copper wire having a diameter of 0.1 mm, and the outermost circumference was made up of 3 turns of 35 mm × 25 mm. A soft magnetic sheet having a size of 37 mm × 27 mm and a thickness of 0.2 mm was used as the substrate 7 for supporting the loop coil 1, and the loop coil 1 was attached with a double-sided tape having a thickness of 0.03 mm. The soft magnetic sheet was provided with an opening at a portion where the terminal portion 2 is disposed. The first electrode plate 3 and the second electrode plate 4 are produced using a single-sided flexible printed board having a conductor layer thickness of 35 μm and a dielectric layer thickness of 75 μm, and are fitted into the opening of the soft magnetic sheet. The end of the loop coil 1 was connected. The sizes of the first electrode plate 3 and the second electrode plate 4 were both 1.5 mm × 3.5 mm.

  The conductive plate is made of aluminum foil having a thickness of 20 μm, and the constant capacity conductive plate 8 having the same size as the first electrode plate 3 and the three adjustment conductive plates 9 for changing the capacitance component are connected by the wiring portion 10. Produced. This conductive plate is formed on the surface opposite to the surface on which the first electrode plate 3 and the second electrode plate 4 of the single-sided flexible printed board are formed, with a double-sided adhesive tape having a thickness of 10 μm. And a second electrode plate 4 so as to face each other. The size of one adjustment conductive plate 9 was 1.5 mm × 1 mm.

  The reactance change rate and resistance value of the antenna element manufactured as described above are measured by cutting the adjustment conductive plate 9 one by one from the constant capacitance conductive plate 8 by cutting the wiring portion 10, and connected to the constant capacitance conductive plate 8. The relationship with the total area of the adjusted conductive plate 9 is obtained.

(Comparative example)
As a comparative example, an antenna element having the configuration shown in FIG. 3 was created and compared. As in the example, the loop coil 1 was made of a copper wire having a diameter of 0.1 mm, and the outermost circumference had three turns of 35 mm × 25 mm. A soft magnetic sheet having a size of 37 mm × 27 mm and a thickness of 0.2 mm was used as the substrate 7 for supporting the loop coil 1, and the loop coil 1 was attached with a double-sided tape having a thickness of 0.03 mm. The soft magnetic sheet was provided with an opening in the same part as in the example. The first electrode plate 3 and the second electrode plate 4 are produced using a single-sided flexible printed board having a conductor layer thickness of 35 μm and a dielectric layer thickness of 75 μm, and are fitted into the opening of the soft magnetic sheet. The end of the loop coil 1 was connected. The sizes of the first electrode plate 3 and the second electrode plate 4 were both 1.5 mm × 3.5 mm.

  The adjustment conductive plate 9 for generating a capacitive component between the antenna pattern of the loop coil 1 is made of an aluminum foil having a thickness of 20 μm, and is formed on the antenna pattern of the loop coil 1 with a double-sided adhesive tape having a thickness of 10 μm. Pasted on.

  The reactance change rate and resistance value of the antenna element manufactured as described above were measured by changing the total area of the adjustment conductive plate 9 attached on the antenna pattern of the loop coil 1.

  FIG. 4 shows the relationship between the total area of the adjustment conductive plate 9 and the reactance change rate. FIG. 5 shows the relationship between the total area of the adjustment conductive plate 9 and the antenna resistance value. 4 and 5, the total area of the adjustment conductive plate 9 is zero. In the embodiment using the configuration of FIG. 2, the adjustment conductive plate 9 is all separated from the constant capacitance conductive plate 8. In the comparative example using the configuration 3, the adjustment conductive plate 9 is completely removed from the antenna pattern of the loop coil 1. As shown in FIG. 4, the embodiment of the present invention can reduce the total area of the adjustment conductive plate 9 required to obtain the same reactance change rate as compared with the comparative example. 5 that the embodiment of the present invention can suppress an increase in the antenna resistance value due to the adjustment conductive plate 9 when the same reactance change rate is obtained.

For example, when the reactance change rate is designed to be 4% based on FIG. 4, the required area of the adjustment conductive plate 9 is 3 mm ² in the embodiment, whereas 105 mm ² is required in the comparative example. I understand that. The antenna resistance value at this time is 1.93Ω in the example, but 3.15Ω in the comparative example, which is about 1.5 times larger than that in the example.

  As described above, according to the present invention, even in an antenna element using a conductor having a small diameter, such as a single wire or a litz wire, characteristic deterioration of the antenna element in reactance adjustment can be reduced.

DESCRIPTION OF SYMBOLS 1 Loop coil 2 Terminal part 3 1st electrode plate 4 2nd electrode plate 5 Insulating substrate 6 Conductive plate 7 Substrate 8 Constant capacity conductive plates 9, 91, 92, 93 Adjustment conductive plate 10 Wiring part

Claims (3)

  A loop coil; a first electrode plate connected to one end of the loop coil; a second electrode plate connected to the other end of the loop coil; an insulating substrate; and a conductive plate. The first electrode plate and the second electrode plate are disposed on one surface of the insulating substrate, the conductive plate is disposed on the other surface of the insulating substrate, and the first electrode plate is disposed on the other surface of the insulating substrate. An antenna element, wherein a projection plane in the thickness direction of the electrode plate and the second electrode plate overlaps at least a part of a projection plane in the thickness direction of the conductive plate.   The conductive plate includes a constant-capacity conductive plate that overlaps at least a portion of the projection surface in the thickness direction with the first electrode plate, and a plurality that overlaps at least a portion of the projection surface in the thickness direction of the second electrode plate. The antenna element according to claim 1, further comprising: an adjustment conductive plate, and a wiring portion that connects the adjustment conductive plate to the constant capacity conductive plate.   The method for manufacturing an antenna element according to claim 2, wherein at least a part of the wiring portion is cut so that a reactance of the antenna element matches a preset value.

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