JP5133607B2 - RFID media - Google Patents

Description

  The present invention relates to an RFID medium having an IC chip that can write and read information in a non-contact state, and in particular, the IC chip is damaged or the connection between the IC chip and the antenna is disconnected. The present invention relates to technology for detecting defects.

  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 contactless IC chip on which information can be written to or read from the card, label, or tag without contact is mounted. IC cards, non-contact type IC labels, or 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 reduce the size and ensure a communicable distance, A fine IC chip that performs communication using the IC is increasingly used.

  When such a fine IC chip is used, information is written to or read from the IC chip by connecting a conductive antenna to the IC chip.

  FIG. 4 is a diagram illustrating an example of a non-contact type IC tag on which an IC chip that performs communication using a microwave band is mounted.

  As shown in FIG. 4, the present configuration example includes two strip-shaped conductor portions 220a and 220b formed on a base substrate 230 made of resin, paper, or the like with a predetermined interval so as to be arranged in series with each other. An antenna 220 is formed, and information can be written and read out in a non-contact state so as to be connected to a feeding point (not shown) provided at one end of each of the two conductor portions 220a and 220b. An IC chip 210 is mounted.

  The non-contact type IC tag 200 configured as described above resonates with radio waves from the information writing / reading device by being brought close to an information writing / reading device (not shown) provided outside. A current flows through the antenna 220 to generate electric power in the antenna 220, and this electric power is supplied to the IC chip 210, whereby information is written from the information writing / reading device to the IC chip 210 in a non-contact state, or an IC Information written in the chip 210 is read out by an information writing / reading device. As described above, in order to write / read information to / from the IC chip 210 by the information writing / reading apparatus, the length of the antenna 220 is set to a frequency for writing / reading information to / from the IC chip 210. It is necessary to set according to the impedance matching between the IC chip 210 and the antenna 220.

  Such a non-contact type IC tag 200 is inspected whether the IC chip 210 operates normally in the manufacturing stage. In addition, an application using the non-contact type IC tag 200 can be performed by inspecting whether the IC chip 210 is not damaged or whether the connection between the IC chip 210 and the antenna 220 is disconnected after the manufacture. Reliability can be improved.

  In such an inspection, when the IC chip 210 is damaged or the connection between the IC chip 210 and the antenna 220 is disconnected, information cannot be written or read. However, as described above, in the non-contact type IC tag 200 as shown in FIG. 4, the information depends on the length of the antenna 220 and whether or not the impedance matching between the IC chip 210 and the antenna unit 220 is taken. Cannot be written or read. Therefore, when inspecting whether the IC chip 210 is damaged or whether the connection between the IC chip 210 and the antenna 220 is disconnected, only writing and reading information using the information writing / reading device is performed. Then, it cannot be said that it can be determined whether the IC chip 210 is damaged or whether the connection between the IC chip 210 and the antenna 220 is broken.

  Here, Patent Document 1 discloses a non-contact data carrier device provided with an impact detection sensor for detecting an impact applied from the outside. This non-contact type data carrier device is provided with an impact detection sensor having a wiring that is disconnected by an impact, and whether or not an impact has been applied by measuring potentials at both ends of the wiring and storing them in the IC chip. Can be stored.

  However, when the impact detection sensor as described above is used, it can be confirmed whether or not an external impact has been applied, but it cannot be recognized whether or not the IC chip is damaged by the impact. Also, when confirming whether or not an impact has been applied, information stored in the IC chip is read out, so that information reading processing for the IC chip is performed, and the IC chip is damaged. It cannot be used for the purpose of detecting that.

  Therefore, a light emitting element circuit using an LED or the like is connected to the antenna in series with the IC chip, and the light emission state of the light emitting element circuit is used to determine whether the IC chip is damaged or the connection between the IC chip and the antenna is broken. It is possible to judge whether or not.

  FIG. 5 is a diagram illustrating an example of a non-contact type IC tag that can detect a defect using a light emitting element circuit.

  As shown in FIG. 5, the present configuration example includes two strip-shaped conductor portions 320a and 320b that are formed on a base substrate 330 made of resin, paper, or the like and have the same length and are arranged in series. An IC chip 310 that can write and read information in a non-contact state so as to be connected to a feeding point (not shown) provided at one end of each of the conductor portions 320a and 320b. Is mounted, and a light emitting element portion 340 having an LED that is turned on by power generated in the antenna 320 is connected to a part of the conductor portion 320b. The length of the antenna 320 in which the two conductor portions 320a and 320b are connected via the IC chip 310 is obtained from the frequency used for writing and reading information, the relative permeability and the relative permittivity of the base substrate 330. It is ½ of the wavelength λ.

  The operation of the non-contact type IC tag 300 configured as described above when the IC chip 310 is damaged will be described.

  6 is a diagram for explaining the operation of the light emitting element unit 340 when the IC chip 310 is damaged in the non-contact type IC tag 300 shown in FIG. The figure which shows the connection state of the antenna 320 when there is no, (b) is a figure which shows the connection state of the antenna 320 when the IC chip 310 is damaged.

  When the IC chip 310 is not damaged in the non-contact type IC tag 300 shown in FIG. 5, the conductor 320a and the conductor 320b constituting the antenna 320 connect the IC chip 310 as shown in FIG. The length of the antenna 320 in which the two conductor portions 320a and 320b are connected via the IC chip 310 is the frequency used for writing and reading information as described above. It is ½ of the wavelength λ obtained from the relative permeability and relative permittivity of the base substrate 330. For this reason, in this state, when the IC chip 310 is brought close to an information writing / reading device for writing or reading information, the antenna 320 performs writing or reading of information from the information writing / reading device. Resonant with the radio wave having the frequency of, current flows to generate electric power, and this electric power is supplied to the light emitting element portion 340 and the light emitting element portion 340 is turned on.

  On the other hand, in the non-contact type IC tag 300 shown in FIG. 5, when the IC chip 310 is damaged due to disconnection of a circuit part built in the IC chip 310, as shown in FIG. The conductor part 320a and the conductor part 320b constituting the antenna 320 are disconnected at the circuit part in the IC chip 310. Therefore, the antenna 320 does not function as a dipole antenna that resonates at a frequency at the resonance point, and no current flows through the antenna 320. As a result, when the IC chip 310 is damaged due to, for example, a circuit part built in the IC chip 310 being disconnected, no power is generated in the antenna 320 and the light emitting element part 340 is not lit.

As described above, when the IC chip 310 is not damaged, when the IC chip 310 is brought close to an information writing / reading apparatus for writing or reading information, information writing from the information writing / reading apparatus is performed. The antenna 320 resonates with a radio wave having a frequency for reading and a current flows through the antenna 320 to generate power. The light emitting element portion 340 is turned on by this power, and the circuit portion in the IC chip 310 is disconnected. For example, when the IC chip 310 is damaged, even if the IC chip 310 is brought close to the information writing / reading device, the antenna 320 generates a radio wave having a frequency for writing and reading information from the information writing / reading device. Does not resonate, and power is not supplied to the light emitting element portion 340 and the light emitting element portion 340 does not light. Therefore, depending on whether the light emitting element portion 340 is lighted, I It is possible to detect whether the chip 310 is damaged.
JP 2002-150249 A

  As shown in FIG. 5, when information is written to or read from the IC chip using only the electric power generated by the antenna and the notification means such as the light emitting element unit is driven, information is sent to the IC chip. It is necessary to supply sufficient power to write or read the data and to supply sufficient power to drive the notification means to the notification means. However, since the electric power generated in the antenna is weaker than that using a power source such as a battery, simply connecting the notification means to a part of the conductor constituting the antenna can drive the notification means. It is difficult to say that sufficient power can be supplied to the notification means. In particular, such IC chips can perform writing and reading of information with weak power, whereas informing means such as light emitting elements are difficult to drive with weak power, and the power generated in the antenna is low. It is desired to supply the notification means efficiently.

  The present invention has been made in view of the problems of the conventional techniques as described above, and is a notification means for detecting whether an IC chip is damaged without using a power source such as a battery. An object of the present invention is to provide an RFID medium that can supply sufficient power to drive the notification means.

In order to achieve the above object, the present invention provides:
An antenna composed of two conductors each having a feeding point, and connected to the feeding point of the two conductors, respectively, and the electric power generated at the antenna is supplied through the feeding point in a non-contact state. In an RFID medium having an IC chip capable of writing and / or reading information,
The two conductors have a bow-tie antenna shape extending in a direction away from the feeding point and extending radially after a predetermined length, and are asymmetrical via the IC chip,
One of the two conductors is connected to a region between the feeding point of the one conductor and extending radially, and has a notifying means that is driven by being supplied with electric power generated by the antenna. To do.
In addition, the notification unit is connected to a conductor having a shorter length from the feeding point to the end opposite to the feeding point, of the two conductors.

  In the present invention configured as described above, when the IC chip is not damaged or the connection between the IC chip and the antenna is not broken, the two conductors constituting the antenna are connected via the IC chip at the feeding point. Therefore, power is generated in the antenna by resonating with the received radio wave, and this power is supplied to the IC chip through the feeding point, so that the IC chip is in a non-contact state. Information writing and reading are performed at. Here, in the vicinity of the feeding point of one of the two conductors constituting the antenna, an informing means that is driven by power supplied from the antenna is connected, the feeding point is Since it is provided in an area where the largest electric power can be obtained among the conductors constituting the antenna, the power generated by the antenna is efficiently supplied to the notification means, and the notification means is driven. On the other hand, when the IC chip is damaged or the connection between the IC chip and the antenna is disconnected, the two conductors constituting the antenna are disconnected by the IC chip. Therefore, no power is generated in the antenna, information is not written to or read from the IC chip, and the notification unit is not driven.

  In this way, the notification means for detecting whether or not the IC chip is damaged is connected in the vicinity of the feeding point of one of the two conductors constituting the antenna, so that the power generated in the antenna Is effectively supplied to the notification means, and even if the power generated by the antenna is weak, it is sufficient to drive the notification means to the notification means without using a power source such as a battery. Power can be supplied.

  As described above, in the present invention, the notification means for detecting whether the IC chip is damaged is connected to the vicinity of the feeding point of one of the two conductors constituting the antenna; Therefore, the power generated in the antenna is efficiently supplied to the notification means, and even if the power generated in the antenna is weak, the notification means is notified without using a power source such as a battery. Sufficient power can be supplied to drive the means.

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

  1A and 1B are diagrams showing an embodiment of an RFID medium according to the present invention, in which FIG. 1A is a top view, FIG. 1B is a diagram showing a detailed configuration of an antenna 120 shown in FIG. FIG. 3 is a circuit diagram showing an internal configuration of a light emitting element unit 140 shown in FIG.

  In the present embodiment, as shown in FIG. 1A, an antenna 120 including two conductor portions 120a and 120b is formed on a base substrate 130 made of resin, paper, or the like, and the two conductor portions 120a and 120b are formed. In addition, the IC chip 110 is connected between the two, and the light emitting element portion 140 serving as notification means is connected to a part of one of the two conductor portions 120a and 120b.

  As shown in FIG. 1B, the conductor portions 120a and 120b are respectively provided with feeding points 121a and 121b for supplying power to the IC chip 110 with a gap between them, and the feeding points 121a and 121b are connected to each other. It has a bow-tie antenna shape that extends in the direction of separation and spreads radially. The IC chip 110 is connected to the feeding points 121a and 121b, so that the two conductor portions 120a and 120b are connected via the IC chip 110. Further, in the conductor portion 120b, the vicinity of the feeding point 121b is electrically opened, and the light emitting element portion 140 is connected to the opened portion. Note that the distance between the feeding point 121b and the light emitting element portion 140 is preferably as short as possible. That is, it is preferable that the electrically open region of the conductor 120b is as close to the feeding point 121b as possible in accordance with the shape of the conductor 120b. In addition, the two conductor portions 120a and 120b have different lengths from the feeding point 120a to the point B in the drawing and from the feeding point 120b to the point B ′ in the drawing, so that the antenna 120 can be connected via the IC chip 110. Is asymmetrical.

  The IC chip 110 has a circuit portion (not shown) such as a memory and a control circuit capable of writing and reading information inside, and two connection terminals (not shown) are provided across the circuit portion. One of the two connection terminals is connected to the feeding point 121a of the conductor part 120a, and the other is connected to the feeding point 121b of the conductor part 120b. Then, power generated in the antenna 120 is supplied to the circuit unit via the feeding points 121a and 121b, whereby information is written or read in a non-contact state.

  As shown in FIG. 1C, the light emitting element unit 140 includes four diodes 142a to 142d constituting the bridge unit 142, two other diodes 144a and 144b, three capacitors 143a to 143c, and an LED 141. The diodes 142a to 142d, 144a and 144b and the capacitors 143a to 143c constitute a rectifier circuit. The two external connection terminals 145 are respectively connected to the electrically opened portions of the conductor portion 120b. An AC current flows through the antenna 120 including the two conductor portions 120a and 120b when the non-contact type IC tag 100 comes close to an information writing / reading device provided outside, and this AC current is stored in the capacitor 143a. ˜143c and diodes 142a to 142d, 144a and 144b are converted into a direct current and supplied to the LED 141. The LED 141 is turned on by the supplied direct current.

  Here, the length of the conductor parts 120a and 120b will be described.

  FIG. 2 is a diagram for explaining the frequency characteristics of the non-contact type IC tag 100 shown in FIG. 1, and the return loss of the non-contact type IC tag 100 with respect to the frequency used for writing / reading information to / from the IC chip 110. Indicates.

In the non-contact type IC tag 100 shown in FIG. 1, as shown in FIG. 2, since the return loss changes depending on the frequency used for writing and reading information, this is the resonance point in the antenna 120 where the return loss is lowest. the frequency at the peak point a, it is necessary to set the frequency f _a used for writing and reading information. Here, the conductor portion 120a, in 120b, a length which is connected via the IC chip 110, obtained from the relative permeability and the relative dielectric constant of the frequency f _a and the base substrate 130 to be used for writing and reading information When it is a multiple of 1/4 of the wavelength λ, it functions as a dipole antenna that resonates at _a frequency at the resonance point, and information can be written to and read from the IC chip 110.

Therefore, in the horizontal direction in the length of the antenna 120, i.e., the length of the two conductor portions 120a, 120b are connected through the IC chip 110, the frequency f _a and the base material used for the writing and reading of data It is 1/4 of the wavelength λ obtained from the relative permeability and relative permittivity of 130. The conductor portions 120a and 120b shown in this embodiment have a bow-tie antenna shape, whereby the length of the two conductor portions 120a and 120b connected via the IC chip 110 is shown in the figure. The length from the point B to the point B ′ in the drawing through the IC chip 110 is the shortest, and the length from the point A in the drawing to the point A ′ in the drawing through the IC chip 110 is the longest. Information is written between the length from point B in the figure through the IC chip 110 to the point B ′ in the figure to the length from point A in the figure to the point in the figure through the IC chip 110. In addition, there is a quarter of the wavelength λ obtained from the frequency f _a used for reading and the relative permeability and relative permittivity of the base substrate 130.

The non-contact type IC tag 100 configured as described above has _a frequency fa from the information writing / reading device by being brought close to an information writing / reading device (not shown) provided outside. A current flows through the antenna 120 composed of the two conductor portions 120a and 120b by resonating with the radio wave to generate power, and this power is supplied to the IC chip 110. Thus, in a non-contact state, the information writing / reading device Information is written to the IC chip 110, and information written to the IC chip 110 is read by an information writing / reading device. Here, in the conductor part 120b, the vicinity of the feeding point 121b is electrically opened, and the light emitting element part 140 is connected to the opened part. Since the feeding point 121b is provided in an area where the largest electric power can be obtained in the conductor 120b when it is brought close to the information writing / reading device, the electric power generated in the antenna 120 is supplied to the light emitting element 140. Efficiently supplied, the light emitting element part 140 is driven and the LED 141 is lit.

  The operation of the light emitting element 140 when the IC chip 110 is damaged or the connection between the IC chip 110 and the antenna 120 is broken in the non-contact type IC tag 100 described above will be described below.

  FIG. 3 illustrates the operation of the light emitting element portion 140 when the IC chip 110 is damaged or the connection between the IC chip 110 and the antenna 120 is broken in the non-contact type IC tag 100 shown in FIG. (A) is a figure which shows the connection state of the antenna 120 when the IC chip 110 is not damaged or the connection between the IC chip 110 and the antenna 120 is not broken, and (b) is the IC chip. It is a figure which shows the connection state of the antenna 120 when 110 is damaged or the connection of the IC chip 110 and the antenna 120 is disconnected.

When the IC chip 110 is not damaged or the connection between the IC chip 110 and the antenna 120 is not broken in the contactless IC tag 100 shown in FIG. 1, the antenna 120 is connected as shown in FIG. The length of the antenna 120 in which the conductor 120a and the conductor 120b are connected to each other via the IC chip 110 and the two conductors 120a and 120b are connected via the IC chip 110 is as follows. , as described above, and has a frequency f _a and 1/4 multiples of the wavelength λ obtained from the relative permeability and the relative dielectric constant of the base material 130 used for writing and reading information. Therefore, in this state, when the IC chip 110 is brought close to an information writing / reading device for writing or reading information, the antenna 120 performs writing or reading of information from the information writing / reading device. _Resonating with a radio wave having _a frequency f _a , a current flows to generate power, and this power is supplied to the IC chip 110 via the feeding points 121a and 121b, and information is written to and read from the IC chip 110. become. At this time, the light emitting element portion 140 is connected to the conductor portion 120b in the vicinity of the feeding point 121b. However, the feeding point 121b is the most of the conductor portion 120b when it is brought close to the information writing / reading device. Since it is provided in a region where a large amount of power can be obtained, the power generated in the antenna 120 is efficiently supplied to the light emitting element portion 140, and the light emitting element portion 140 is driven to turn on the LED 141.

On the other hand, in the non-contact type IC tag 100 shown in FIG. 1, when the IC chip 110 is damaged or the connection between the IC chip 110 and the antenna 120 is broken, as shown in FIG. The conductor 120a and the conductor 120b constituting the antenna 120 are disconnected at the point where the IC chip 110 is connected. Therefore, the antenna 120, no longer functions as a dipole antenna the frequency at the resonance point resonates becomes f _a, in this state, close to the information writing / reading device for writing and reading information to the IC chip 110 Even if it does, current does not flow through the antenna 120, information is not written to or read from the IC chip 110, the light emitting element portion 140 is not driven, and the LED 141 in the light emitting element portion 140 is not lit.

As described above, when the IC chip 110 is not damaged or the connection between the IC chip 110 and the antenna 120 is not disconnected, an information writing / reading apparatus that writes information to or reads information from the IC chip 110 is used. When close to each other, the antenna 120 resonates with a radio wave having _a frequency fa for writing and reading information from the information writing / reading device, and a current flows through the antenna 120 to generate electric power. If the LED 141 in the unit 140 is lit, and the IC chip 110 is damaged or the connection between the IC chip 110 and the antenna 120 is broken, the information can be read even if it is brought close to the information writing / reading device. Telecommunications without resonance antenna 120 having a frequency f _a for writing and reading information from the write / read device, the light-emitting device 140 Since power is not supplied and the LED 141 in the light emitting element unit 140 is not lit, whether the IC chip 110 is damaged or the connection between the IC chip 110 and the antenna 120 is disconnected depending on whether the LED 141 is lit. Can be detected. Then, the light emitting element portion 140 for detecting whether the IC chip 110 is damaged or the connection between the IC chip 110 and the antenna 120 is disconnected is used as the IC chip 110 in the conductor portion 120b constituting the antenna 120. Is connected to the vicinity of the feeding point 121b for supplying power to the IC chip 110, the power generated in the antenna 120 is efficiently supplied to the light emitting element part 140, and the LED 141 in the light emitting element part 141 is connected. Can be lit easily.

  Accordingly, the electromotive force of the light emitting element unit 140 can easily turn on the LED 141 in the light emitting element unit 141, but the antenna 120 resonates with the radio wave from the information writing / reading device, so that the antenna 120 It is possible to use the generated electric power, and it is not necessary to incorporate a power source such as a battery for turning on the LED 141 in the light emitting element unit 141 in the non-contact type IC tag 100, and maintenance such as battery exhaustion is unnecessary. Become.

In this embodiment, the lengths of the two conductor portions 120a and 120b from the feeding points 121a and 121b to the other end of the bow tie antenna shape are different from each other, so that the antenna 120 is asymmetrical via the IC chip 110. However, in the present invention, the antenna 120 may be symmetrical with respect to the IC chip 110 because the two conductor portions 120a and 120b have the same shape. . However, when the antenna 120 is asymmetrical via the IC chip 110, the length from the feeding point 121b of the conductor 120b to the other end of the bow tie antenna shape is used for writing and reading information. Since the frequency f _a and the relative permeability and relative permittivity of the base substrate 130 do not become ½ ⁿ (n is a natural number) of the wavelength λ, the frequency at the resonance point of the conductor portion 120b is f _a . The LED 141 in the light emitting element section 140 is turned on when the IC chip 110 is damaged or the connection between the IC chip 110 and the antenna 120 is broken. It is possible to reliably prevent malfunctions that occur.

In this embodiment, the length of the two conductor portions 120a and 120b connected via the IC chip 110 is such that the frequency fa used for writing and reading information and the relative permeability and relative dielectric of the base substrate 130 are as _follows. While a quarter of the wavelength lambda obtained from the rates, write and 1/4 multiples of the frequency f _a and the wavelength obtained from the relative permeability and the relative dielectric constant of the base material 130 lambda used for reading information If it is.

  Further, in this embodiment, the LED 141 that is turned on by the electric power generated in the antenna 120 has been described as an example as a means for notifying when the information is written to or read from the IC chip 110. It is also conceivable to use a vibrator that vibrates by the electric power generated in the antenna 120, a buzzer that generates sound by the electric power generated in the antenna 120, or the like as the notification means.

  In addition, the two conductor portions 120a and 120b constituting the antenna 120 are not limited to the shape of the bow tie antenna, and may be linear or meandered as long as the length satisfies the above-described conditions. Etc.

  In this embodiment, the non-contact type IC tag is described as an example of the RFID medium. However, it is needless to say that the present invention can be applied to a non-contact type IC card and a non-contact type IC label.

It is a figure which shows one Embodiment of RFID media of this invention, (a) is a top view, (b) is a figure which shows the detailed structure of the antenna shown to (a), (c) is a figure (a). It is a circuit diagram which shows the internal structure of the shown light emitting element part. It is a figure for demonstrating the frequency characteristic of the non-contact-type IC tag shown in FIG. It is a figure for demonstrating operation | movement of the light emitting element part in case the IC chip is damaged in the non-contact type IC tag shown in FIG. 1, or the connection of an IC chip and an antenna is disconnected, (a) Is a diagram showing the connection state of the antenna when the IC chip is not damaged or the connection between the IC chip and the antenna is not broken, and (b) is the broken IC chip or the connection between the IC chip and the antenna is broken. It is a figure which shows the connection state of the antenna in the case of doing. It is a figure which shows an example of the non-contact-type IC tag carrying the IC chip which communicates using a microwave band. It is a figure which shows an example of the non-contact-type IC tag which can detect a malfunction using a light emitting element circuit. FIG. 6 is a diagram for explaining the operation of the light emitting element portion when the IC chip is damaged in the non-contact type IC tag shown in FIG. 5, and (a) shows the connection state of the antenna when the IC chip is not damaged. FIG. 4B is a diagram showing the connection state of the antenna when the IC chip is damaged.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Non-contact-type IC tag 110 IC chip 120 Antenna 120a, 120b Conductor part 121a, 121b Feeding point 130 Base base material 140 Light emitting element part 141 LED
142 Bridge part 143a-143c Capacitor 142a-142d, 144a, 144b Diode 145 External connection terminal

Claims (2)

An antenna composed of two conductors each having a feeding point, and connected to the feeding point of the two conductors, respectively, and the electric power generated at the antenna is supplied through the feeding point in a non-contact state. In an RFID medium having an IC chip capable of writing and / or reading information,
The two conductors have a bow-tie antenna shape extending in a direction away from the feeding point and extending radially after a predetermined length, and are asymmetrical via the IC chip,
One of the two conductors is connected to a region between the feeding point of the one conductor and extending radially, and has a notifying means that is driven by being supplied with electric power generated by the antenna. RFID media.   The RFID media of claim 1, wherein
  The informing means is an RFID medium connected to a conductor having a shorter length from the feeding point to the end opposite to the feeding point of the two conductors.

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