JP4708155B2 - Broadband antenna - Google Patents

Description

  The present invention relates to a broadband antenna having a broadband characteristic, and more particularly to a technique for reducing the size while realizing a broadband.

  In recent years, with the progress of the information society, information is recorded on a card, and information management and settlement using the card are performed. Information is recorded on a label or tag attached to a product or the like, and the product or the like is managed using the label or tag.

  In information management using such a card, label, or tag, a non-contact type equipped with an IC capable of writing and reading information in a non-contact state on the card, label, or tag. IC cards, non-contact type IC labels, and non-contact type IC tags are rapidly spreading due to their excellent convenience.

  In a non-contact type IC card, a non-contact type IC label, and a non-contact type IC tag that can write and read information in a non-contact state, in recent years, in order to ensure downsizing and a communicable distance, 900 MHz to 1000 MHz. Fine IC chips that use the frequency band of the communication to start communication are beginning to be used.

  When such a fine IC chip is used, the communicable distance of the IC chip can be extended by connecting a conductive antenna to the IC chip.

  FIG. 8 is a diagram illustrating an example of a non-contact type IC tag on which an IC chip that performs communication using a frequency band of 900 MHz to 1000 MHz is mounted, in which (a) is a top view and (b) is (a). It is AA 'sectional drawing shown in FIG.

  As shown in FIG. 8, the present configuration example is composed of two strip-like conductors 210a and 210b formed on a base substrate 202 made of resin, paper, or the like with a predetermined interval so as to be arranged in series with each other. An antenna portion 210 is formed, and an IC chip 201 capable of writing and reading information in a non-contact state is mounted so as to be connected to the two conductors 210a and 210b.

  In the non-contact type IC tag 200 configured as described above, the antenna unit 210 is caused by radio waves from the information writing / reading device by being brought close to an information writing / reading device (not shown) provided outside. Current is supplied to the IC chip 201, whereby information is written to the IC chip 201 from the information writing / reading device in a non-contact state, or information written to the IC chip 201 is Or read by a writing / reading device.

  In such a non-contact type IC tag 200, it is necessary to perform impedance matching between the IC chip 201 and the antenna unit 210 in order to secure a distance at which information can be written to and read from the IC chip 201. Therefore, the length of the antenna unit 210 is set according to the frequency of writing and reading information to the IC chip 201. Therefore, when the contactless IC tag 200 is miniaturized, the limit is determined by the frequency of information writing and reading to the IC chip 201.

  Here, a meander antenna has been used in the past that can reduce the size of the entire antenna while increasing the length of the antenna by making the belt-like antenna into a zigzag shape (see, for example, Patent Document 1). ). By using this meander antenna, it is possible to reduce the size of the non-contact type IC tag 200 while setting the length of the antenna unit 210 in accordance with the frequency of writing and reading information with respect to the IC chip 201.

  By the way, the non-contact type IC tag 200 as described above may be used by being attached to a metal or the like. In this case, the resonance frequency in the antenna unit 210 is reduced to an IC chip due to deterioration of communication characteristics due to the influence of the metal. The frequency of writing / reading information to / from 201 shifts, making it impossible to write / read information to / from the non-contact type IC tag 200, or securing a stable communication distance. There is a fear.

  As a technique for dealing with such a frequency shift, a bow tie antenna is used in which two triangular conductors are arranged so that their apexes face each other through a gap.

  9A and 9B are diagrams showing an example of a non-contact type IC tag having a general bow tie antenna. FIG. 9A is a top view, and FIG. 9B is a cross-sectional view taken along line A-A ′ shown in FIG.

  In this example, as shown in FIG. 9, two conductors 310 a and 310 b having an isosceles triangle shape connect bases 302 made of resin, paper, or the like, with apexes formed by equal sides of an isosceles triangle. An antenna portion 310 is formed so that the straight line is perpendicular to each of the bases of the isosceles triangles and the vertices have a gap, and the two conductors 310a and 310b are formed. In order to be connected, an IC chip 301 capable of writing and reading information in a non-contact state is mounted.

In the non-contact type IC tag 300 configured as described above, the length of the antenna unit 310 differs between BB ′ and CC ′, and the length is BB ′. The impedance of the antenna unit 310 changes from the impedance based on the length between BB ′ to the impedance based on the length between CC ′. It can be set. In this way, a broadband antenna can be realized using a bow tie antenna (see, for example, Patent Document 2).
JP 2003-78335 A JP 2002-135037 A

  However, when the above-described bow tie antenna is used for a non-contact type IC tag, a wide-band antenna can be realized, but the entire antenna, and hence the non-contact type IC tag cannot be downsized. There is a problem that.

  The present invention has been made in view of the problems of the conventional techniques as described above, and an object of the present invention is to provide a broadband antenna that can be downsized while realizing a broadband.

In order to achieve the above object, the present invention provides:
A wideband antenna comprising two conductors each having a feeding point facing each other with a gap therebetween,
At least one of the two conductors spreads radially in a direction away from the feeding point, and a plurality of bowtie antenna portions having two vertices on the opposite side to the feeding point are connected in a direction away from the feeding point. Become.

  In the present invention configured as described above, a wide band is realized by the bow tie antenna unit that constitutes at least one of the two conductors each having a feeding point facing each other via a gap. The length of the conductor formed by connecting a plurality of bow tie antennas is the length of the path through which one of the two apexes of the plurality of bow tie antennas passes, and the conductor appears as an antenna. The upper length becomes longer. This makes it possible to increase the apparent length of the conductor as an antenna while reducing the size of the entire antenna. Here, since the resonance frequency becomes lower as the length of the conductor as an antenna becomes longer, if the overall size of the antenna is the same size, by increasing the apparent length of the conductor as an antenna, The resonance frequency can be shifted to the low frequency side.

  It is also conceivable that a plurality of bow tie antenna units are alternately connected to one of the two apexes of the bow tie antenna unit connected to the feed point side in a direction away from the feed point. In that case, the length of the conductor formed by connecting a plurality of bow tie antenna portions is the length of the path where the shortest portion alternately passes one of the two vertices of the plurality of bow tie antenna portions, and the desired frequency. Therefore, the antenna as a whole can be further reduced in size. Further, if the size of the entire antenna is the same, the resonance frequency can be further shifted to the lower frequency side.

  As described above, in the present invention, at least one of the two conductors each having a feeding point facing each other through a gap is spread radially in a direction away from the feeding point and 2 on the side opposite to the feeding point. Since a plurality of bow tie antenna portions having one apex are connected in a direction away from the feeding point, the size can be reduced while realizing a wide band. Further, if the size of the entire antenna is the same, the resonance frequency can be shifted to the low frequency side.

  Embodiments of the present invention will be described below with reference to the drawings.

(First embodiment)
FIG. 1 is a diagram showing a first embodiment of a broadband antenna according to the present invention.

  In this embodiment, as shown in FIG. 1, two conductors 10a and 10b are arranged so as to be arranged in series via a gap. The two conductors 10a and 10b are provided with feeding points 11a and 11b, respectively, and the feeding points 11a and 11b are opposed to each other through a gap. The two conductors 10a and 10b are connected in the direction away from the feed points 11a and 11b, and the five bow tie antenna portions 12a and 12b radially extending in the direction away from the feed points 11a and 11b, respectively. Are connected and configured. The connection positions of the five bow tie antenna portions 12a and 12b with the bow tie antenna portions 12a and 12b or the resistance adjustment portions 13a and 13b connected to the opposite sides of the feeding points 11a and 11b are the bow tie antenna portions 12a and 12b, respectively. It is the position of the midpoint of the two vertices on the opposite side to the feeding point 11a, 11b of 12b.

  The apparent length of the conductors 10a and 10b as the antenna in the broadband antenna 10 configured as described above will be described below. In the following description, the five bow tie antenna portions 12a and 12b constituting the conductors 10a and 10b are respectively connected to the first stage, the second stage, the third stage, and the third stage from the feeding points 11a and 11b. It is referred to as the fourth, fourth and fifth stages.

  The length of the shortest part from the feeding point 11a of the conductor 10a to the resistance adjusting unit 13a is a continuous contact point between the first-stage bow tie antenna unit 12a and the second-stage bow tie antenna unit 12a, as shown by a broken line in the figure. Connection point between the second-stage bow tie antenna unit 12a and the third-stage bow tie antenna unit 12a, connection point between the third-stage bow tie antenna unit 12a and the fourth-stage bow tie antenna unit 12a, and the fourth-stage bow tie It becomes the length of a straight line connecting the feed point 11a and the continuous contact point between the fifth-stage bow tie antenna part 12a and the resistance adjusting part 13a via the continuous contact point between the antenna part 12a and the fifth-stage bow tie antenna part 12a. .

  Further, the length of the longest portion from the feeding point 11a of the conductor 10a to the resistance adjusting unit 13a is as shown by a two-dot chain line in the figure from the feeding point 11a of the conductor 10a to the first-stage bow tie antenna unit 12a. A single contact point between the first-stage bow tie antenna unit 12a and the second-stage bow tie antenna unit 12a is reached via one vertex, and from this continuous contact, one vertex of the second-stage bow tie antenna unit 12a is reached. The second-stage bow tie antenna unit 12a and the third-stage bow tie antenna unit 12a reach a continuous contact point, and the third-stage bow tie antenna unit 12a passes through one vertex of the third-stage bow tie antenna unit 12a. The fourth-stage bow tie antenna 12a and the fourth-stage bow-tie antenna section 12a, and the fourth-stage bow-tie antenna section 12a is connected to the fourth-stage bow-tie antenna section 12a. 12a and the fifth-stage bow tie antenna section 12a are reached, and the fifth-stage bow tie antenna section 12a and the resistance adjusting section 13a are connected to the fifth-stage bow tie antenna section 12a through one vertex of the continuous contact. It is the length of the path to reach the contact point.

  The conductor 10b is the same as the conductor 10a.

  Thus, the length of the conductors 10a and 10b formed by connecting the five bow tie antenna portions 12a and 12b is the length of the path through which the longest portion passes one of the two vertices of the bow tie antenna portions 12a and 12b. The apparent length of the conductors 10a and 10b as an antenna becomes longer. Thereby, it is possible to increase the apparent length of the conductors 10a and 10b as the antenna while reducing the size of the entire broadband antenna 10.

(Second Embodiment)
FIG. 2 is a diagram showing a second embodiment of the wideband antenna of the present invention.

  In this embodiment, as shown in FIG. 2, two conductors 110a and 110b are arranged so as to be arranged in series via a gap. The two conductors 110a and 110b are provided with feeding points 111a and 111b, respectively, and the feeding points 111a and 111b are opposed to each other through a gap. The two conductors 110a and 110b are connected in the direction away from the feed points 111a and 111b by the five bowtie antenna portions 112a and 112b that spread radially in the direction away from the feed points 111a and 111b, respectively. Are connected and configured. The connection positions of the five bow tie antenna portions 112a and 112b with the bow tie antenna portions 112a and 112b or the resistance adjustment portions 113a and 113b connected to the opposite sides of the feeding points 111a and 111b are the bow tie antenna portions 112a and 112b, respectively. One vertex of the two vertices on the opposite side to the feeding points 111a and 111b of 112b, and the vertexes connected to each other among the two vertices are alternately arranged for the five bowtie antenna portions 112a and 112b.

  The apparent length of the conductors 110a and 110b as the antenna in the broadband antenna 10 configured as described above will be described below. In the following description, the five bow tie antenna portions 112a and 112b constituting the conductors 110a and 110b are respectively connected to the first stage, the second stage, the third stage, and the third stage from the feeding points 111a and 111b. It is referred to as the fourth, fourth and fifth stages.

  The length of the shortest portion from the feeding point 111a of the conductor 110a to the resistance adjusting portion 113a is a continuous contact point between the first-stage bow tie antenna portion 112a and the second-stage bow tie antenna portion 112a, as shown by a broken line in the figure. Connection point between second-stage bow tie antenna portion 112a and third-stage bow tie antenna portion 112a, connection point between third-stage bow tie antenna portion 112a and fourth-stage bow tie antenna portion 112a, and fourth-stage bow tie This is the length of the path from the feeding point 111a to the resistance adjusting unit 113a through only the continuous contact point between the antenna unit 112a and the fifth-stage bow tie antenna unit 112a.

  Further, the length of the longest portion from the feeding point 111a of the conductor 110a to the resistance adjusting unit 113a is, as shown by a two-dot chain line in the figure, from the feeding point 111a of the conductor 110a to the first-stage bow tie antenna unit 112a. The connection point between the first-stage bow tie antenna unit 112a and the second-stage bow tie antenna unit 112a is reached via an apex that is not the connection unit, and is not a connection unit of the second-stage bow tie antenna unit 112a from this connection point. It reaches the connection point between the second-stage bow tie antenna unit 112a and the third-stage bow tie antenna unit 112a via the apex, and passes through the apex that is not the connection part of the third-stage bow tie antenna unit 112a. The third stage bow tie antenna unit 112a and the fourth stage bow tie antenna unit 112a reach the connection point, and the fourth stage bow tie The fourth stage bow tie antenna part 112a and the fifth stage bow tie antenna part 112a are reached via a vertex that is not a connected part of the tena part 112a, and the fifth stage bow tie antenna part 112a is connected to the fifth stage bow tie antenna part 112a. This is the length of the path that reaches the connection point between the fifth-stage bow-tie antenna unit 112a and the resistance adjustment unit 113a via a vertex that is not a connection part.

  The conductor 110b is the same as the conductor 110a.

  Thus, with respect to what is shown in the first embodiment, the length of the shortest part from the feeding points 111a, 111b of the conductors 110a, 110b to the resistance adjusting parts 113a, 113b, and the length of the longest part. Since both the lengths are increased, the apparent length of the conductors 110a and 110b as the antenna can be further increased while the entire broadband antenna 110 is reduced in size.

  Note that the resistance adjusters 13a, 13b, 113a, and 113b in the two embodiments described above adjust the resistance values of the conductors 10a, 10b, 110a, and 110b, and are not necessarily provided.

  Further, it is also conceivable that only one of the two conductors constituting the broadband antennas 10 and 110 is configured such that the bow tie antenna unit is connected, and the other is a conductor composed of a solid pattern or a lattice pattern having an arbitrary shape. It is done.

  Hereinafter, impedance characteristics when the above-described two embodiments are applied to a non-contact type IC tag will be described as examples.

Example 1
3A and 3B are diagrams showing a non-contact type IC tag using the broadband antenna 10 shown in FIG. 1, wherein FIG. 3A is a diagram showing a stacked state, and FIG. 3B is a configuration of the inlet 20 shown in FIG. FIG.

  In this embodiment, as shown in FIG. 3, the foamed substrate 30 is attached to the inlet 20 having the broadband antenna 10 shown in FIG. 1 by the adhesive 40, and the metal layer 50 is attached to the foamed substrate 30 by the adhesive 40. It is configured to be worn. The inlet 20 has the broadband antenna 10 shown in FIG. 1 formed on a resin sheet 21 such as PET, and the broadband antenna 10 is provided at feeding points 11 a and 11 b provided on the two conductors 10 a and 10 b constituting the broadband antenna 10. An IC chip 22 capable of writing and reading information in a non-contact state is connected via 10. The foam substrate 30 is made of a foam resin having a thickness of 5 mm, and the metal layer 50 is made of a 35 μm thick metal foil made of copper.

  The impedance characteristics of the non-contact type IC tag configured as described above will be described below. In this embodiment, the impedance characteristic of the non-contact type IC tag shown in FIG. 3 is compared with the impedance characteristic of the non-contact type IC tag shown in FIG. At that time, the non-contact type IC tag shown in FIG. 9 is used as an inlet, and the foamed substrate 30 and the metal layer 40 are pasted using the adhesive 40 in the same manner as the non-contact type IC tag shown in FIG. To do. In addition, the shapes of the broadband antenna 10 and the antenna unit 310 are the same of 14 mm × 172.8 mm, and the tag sizes are the same of 20 mm × 178.8 mm.

  FIG. 4 is a diagram for explaining impedance characteristics of the non-contact type IC tag shown in FIG.

  Under the conditions described above, the contactless IC tag shown in FIG. 9 has an impedance curve peak near 1.15 GHz as shown in FIG. The non-contact type IC tag has an impedance curve peak in the vicinity of 1.0 GHz, as indicated by A in FIG.

  As described above, the non-contact type IC tag shown in FIG. 3 has the impedance curve peak shifted to the low frequency side with respect to the non-contact type IC tag shown in FIG. This is because the resonance frequency becomes lower as the length of the conductor as an antenna becomes longer, and the apparent length as the antenna of the broadband antenna 10 of the non-contact IC tag shown in FIG. Since the length of the antenna unit 310 shown in FIG. 9 is longer, the resonance frequency is shifted to the low frequency side.

(Example 2)
5A and 5B are diagrams showing a non-contact type IC tag using the broadband antenna 110 shown in FIG. 2, wherein FIG. 5A is a diagram showing a stacked state, and FIG. 5B is a configuration of the inlet 120 shown in FIG. FIG.

  In this embodiment, as shown in FIG. 5, the foam substrate 30 is attached to the inlet 120 having the broadband antenna 110 shown in FIG. 2 by the adhesive 40, and the metal layer 50 is attached to the foam substrate 30 by the adhesive 40. It is configured to be worn. The inlet 120 has the broadband antenna 110 shown in FIG. 2 formed on a resin sheet 21 such as PET, and the broadband antenna is provided at the feeding points 111 a and 111 b provided on the two conductors 110 a and 110 b constituting the broadband antenna 110, respectively. An IC chip 22 capable of writing and reading information in a non-contact state is connected via 110. The foam substrate 30 is made of a foam resin having a thickness of 5 mm, and the metal layer 50 is made of a 35 μm thick metal foil made of copper.

  The impedance characteristics of the non-contact type IC tag configured as described above will be described below. In this embodiment, the non-contact type IC tag shown in FIG. 5 is compared with the non-contact type IC tag shown in FIG. At that time, the non-contact type IC tag shown in FIG. 9 is used as an inlet, and the foamed substrate 30 and the metal layer 40 are pasted using the adhesive 40 in the same manner as the non-contact type IC tag shown in FIG. To do.

  FIG. 6 is a diagram showing the size when the impedance characteristics of the non-contact type IC tag shown in FIGS. 5 and 9 are measured.

  For the non-contact type IC tag shown in FIG. 5, the broadband antenna 110 having a shape of 14 mm × 172.8 mm and a tag size of 20 mm × 178.8 mm was designated as A. For the non-contact type IC tag shown in FIG. 9, the shape of the antenna unit 310 is 14 mm × 232.8 mm, the tag size is 20 mm × 238.8 mm is B, and the shape of the antenna unit 310 is Was 14 mm × 172.8 mm, and C was a tag size of 20 mm × 178.8 mm.

  FIG. 7 is a diagram for explaining the impedance characteristics of the non-contact type IC tag under the conditions shown in FIG. 6, (a) is a diagram showing the impedance characteristics of the real part, and (b) is the imaginary part. The figure which shows an impedance characteristic, (c) is an enlarged view of 0.9 GHz vicinity of the impedance characteristic shown to (a).

  As shown in FIG. 7, when the non-contact type IC tag shown in FIG. 5 and the non-contact type IC tag shown in FIG. 9 have the same size, the non-contact type IC tag shown in FIG. As shown in C in FIG. 7, one peak of the impedance curve exists near 1.15 GHz, whereas the non-contact type IC tag shown in FIG. 5 has 0 as shown in A in FIG. There is one peak in the impedance curve near 85 GHz.

  Thus, the non-contact type IC tag shown in FIG. 5 has the impedance curve peak shifted to the lower frequency side than the non-contact type IC tag shown in FIG. This is because the resonance frequency becomes lower as the length of the conductor antenna becomes longer. The length of the broadband antenna 110 of the non-contact IC tag shown in FIG. Since it is longer than the length of the antenna unit 310 shown, the resonance frequency is shifted to the low frequency side. As a result, the resonance frequency of the non-contact type IC tag shown in FIG. 5 is shifted to the lower frequency side than the non-contact type IC tag shown in FIG. As described above, in recent years, an IC chip that performs communication using a frequency band of 900 MHz to 1000 MHz is used. Therefore, the contactless IC tag shown in FIG. 5 is stable in this frequency band. It is possible to secure the communication distance.

  Further, when the non-contact type IC tag shown in FIG. 9 is made larger than the non-contact type IC tag shown in FIG. 5, the frequency at which the peak of the impedance curve exists is shown in FIG. It is almost the same as that of the non-contact type IC tag shown. That is, the non-contact type IC tag shown in FIG. 9 has a shape larger than that of the non-contact type IC tag shown in FIG. 5 in order to perform communication using a frequency band of 900 MHz to 1000 MHz. This means that the non-contact type IC tag shown in FIG. 5 can be downsized.

  In addition, as shown in FIG. 7C, in the frequency band of 900 MHz to 1000 MHz, the slope of the impedance curve between the non-contact IC tag shown in FIG. 5 and the non-contact IC tag shown in FIG. Are equal. This indicates that the non-contact type IC tag shown in FIG. 5 can secure a band even though the non-contact type IC tag shown in FIG. 9 is downsized.

  In this way, the non-contact type IC tag shown in FIG. 5 can be downsized while realizing a wide band.

  As for directivity, the metal layer 50 functions as a reflector and has a large directivity on the inlet 120 side.

It is a figure which shows 1st Embodiment of the wideband antenna of this invention. It is a figure which shows 2nd Embodiment of the wideband antenna of this invention. It is a figure which shows the non-contact-type IC tag using the wideband antenna shown in FIG. 1, (a) is a figure which shows a lamination | stacking state, (b) is a figure which shows the structure of the inlet 20 shown to (a). . It is a figure for demonstrating the impedance characteristic of the non-contact-type IC tag shown in FIG. It is a figure which shows the non-contact-type IC tag using the broadband antenna shown in FIG. 2, (a) is a figure which shows a lamination | stacking state, (b) is a figure which shows the structure of the inlet shown to (a). It is a figure which shows the size at the time of measuring the impedance characteristic of the non-contact-type IC tag shown in FIG.5 and FIG.9. 7A and 7B are diagrams for explaining impedance characteristics of the non-contact type IC tag under the conditions shown in FIG. 6, where FIG. 7A shows the impedance characteristics of the real part, and FIG. 7B shows the impedance characteristics of the imaginary part. FIG. 4C is an enlarged view in the vicinity of 0.9 GHz of the impedance characteristic shown in FIG. It is a figure which shows an example of the non-contact-type IC tag by which the IC chip which communicates using the frequency band of 900 MHz-1000 MHz is mounted, (a) is a top view, (b) is A shown to (a). It is -A 'sectional drawing. It is a figure which shows an example of the non-contact-type IC tag which has a general bow-tie antenna, (a) is a top view, (b) is A-A 'sectional drawing shown to (a).

Explanation of symbols

10, 110 Broadband antennas 10a, 10b, 110a, 110b Conductors 11a, 11b, 111a, 111b Feed points 12a, 12b, 112a, 112b Bowtie antenna units 13a, 13b, 113a, 113b Resistance adjustment units 20, 120 Inlet 21 Resin sheet 22 IC chip 30 Foamed substrate 40 Adhesive 50 Metal layer

Claims (1)

A wideband antenna comprising two conductors each having a feeding point facing each other with a gap therebetween,
At least one of the two conductors spreads radially in a direction away from the feeding point, and a plurality of bowtie antenna portions having two vertices on the opposite side to the feeding point are connected in a direction away from the feeding point. A wideband antenna.

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