JP2008306689A - Booster antenna - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a booster antenna which is provided in a compact case and can have a longer communication distance and a wider communicable range in a different direction even when a transmitting/receiving antenna has a small diameter. <P>SOLUTION: The booster antenna has a transmitting/receiving antenna 12 for information to and from a contactless RFID card in a case 20, a control IC 14 etc., which processes information sent and received through the transmitting/receiving antenna 12, and the case 20 containing the transmitting/receiving antenna 12 and the control IC 14 etc. The case 20 is provided with a resonance antenna coil 23 having a larger diameter than the transmitting/receiving antenna 12. A magnetic member 22 is disposed between the transmitting/receiving antenna 12 and resonance antenna 23. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention is provided in an RFID reader / writer that can read and write information without contact with an RFID card by being attached to or detached from an external device such as a personal computer. For example, the communication distance can be increased by using a resonant antenna. The present invention relates to a booster antenna that can be miniaturized without sacrificing.

  In recent years, an IC chip that can store information electronically, and a system using a card or a tag that includes an interface for exchanging information between the IC chip and the outside, has attracted attention because of its various possibilities. Collecting. Such a system is generally referred to as an RFID (Radio Frequency Identification) system. By combining a small recording medium (card or tag) with a reader / writer that reads and writes data on the recording medium, it is possible to perform solid-state authentication in various situations. It can be used to send and receive data.

  As for a small-sized recording medium, there are various names such as an RFID card, an IC card, a wireless card, an RFID tag, and an IC tag. In the present invention, although referred to as an RFID card, it is not intended to be limited to a specific type, but is a broad concept including all the above cards, tags, and the like. Since such an RFID card can store a large amount of information in the memory of the IC chip and prevent counterfeiting, compared with the magnetic recording type used in conventional cards, Widely used as credit cards, electronic money, electronic tickets, telephone cards, ID cards, cargo management tags, and the like.

  As a method for transmitting and receiving information to and from the reader / writer, a contact type in which an electrode contact provided on the surface of the RFID card and a contact terminal provided on the reader / writer are brought into contact with each other, an RFID card and a reader / writer are used. There is a non-contact type that is performed wirelessly through an antenna (coil) provided. In particular, non-contact type RFID cards have high durability because they do not wear due to contact, do not require a mechanism to move the RFID card to the reader / writer, and have a high degree of freedom in direction during transmission and reception. It is expected to spread as something with convenience.

  Furthermore, as a reader / writer that performs such reading and writing, from a fixed type installed at a cash register of a store or a ticket gate of a station, a small handy type that can be used by hand (see Patent Document 1), etc. Various things are used.

  By the way, when introducing the RFID system as described above, it is desirable to be able to effectively utilize applications, databases, hardware, and the like of existing management systems. In addition, a reader / writer that reads / writes an RFID card is preferably inexpensive and small so that it can be freely moved and used in various bases such as ports, airports, factories, and shops.

  However, since a conventional reader / writer for an RFID card is configured as a dedicated device, the cost for newly introducing the device increases. Even if the reader / writer is reduced in size, it is necessary to increase the size of the antenna in order to ensure versatility for use and secure a communication distance (see Patent Document 1). A form of connection with a notebook personal computer or the like is also conceivable. However, when a reader / writer and a large antenna are connected to the notebook personal computer, it is difficult to carry around and it is not always easy to use while moving.

  From such a viewpoint, as shown in Patent Document 2, the present applicant transmits / receives data via a connector for connection with an external device, an antenna for transmitting / receiving information to / from a non-contact RFID card, and the antenna. In a RFID reader / writer having a control unit for processing information, a connector is disposed on one end side of the reader / writer main body, and an antenna is disposed near the end opposite to the connector. .

In the invention of Patent Document 2 as described above, since the antenna is at the opposite end to the connector, when the connector is connected to the external device, a long distance between the external device and the antenna can be secured, and the RFID card When the antenna is brought close to the antenna, an external device does not get in the way, and sufficient reception sensitivity can be obtained.
JP 2004-180039 A JP 2006-85288 A JP 2005-323019 A

  By the way, the invention of Patent Document 2 makes it possible to reduce the size of the RFID reader / writer by integrating the connector. However, since the size of the transmission / reception antenna is limited to the size of the RFID reader / writer, particularly when the RFID reader / writer is in a stick shape, a large-diameter antenna cannot be prepared. The communication distance is short.

  In particular, the RFID reader / writer of Patent Document 2 is often used by being directly inserted into a USB terminal of a personal computer by providing a USB terminal as a connector. In this case, the communication distance is short as described above. In a state where a personal computer is placed on a table or the like, data must be exchanged by bringing the RFID card close to the RFID reader / writer until it almost comes into contact.

  In order to cope with this, as shown in Patent Document 3, it has also been proposed to provide a booster antenna close to the RFID card side. However, providing a booster antenna on the RFID card attached to the product is not small enough if the product itself is large or a booster antenna can be provided in the product storage, and it is small enough to be incorporated in the product tag This RFID card was not applicable.

  Further, a resonant antenna coil as a booster antenna can be built in the RFID reader / writer side. For example, as shown in FIG. 10, it is conceivable to attach a resonant antenna coil 23 to the inner surface of the case 20 at the top of the transmission / reception antenna 12 or to embed the resonant antenna coil 23 in the case 20 as shown in FIG. 11. . In such a case, the communication distance can be extended by increasing the diameter of the resonant antenna coil 23 as much as possible.

  However, as shown in FIGS. 10 and 11, inside the RFID reader / writer, the circuit pattern of the substrate 10 and parts using metal disposed on the substrate 10 (the leads of the control IC 14 and the oscillator) 13 and connector 11). If such a metal part exists below the resonant antenna coil 23, the communication distance cannot be sufficiently extended due to the influence of the metal part.

  The direction of the USB terminal of the personal computer may be vertical or horizontal depending on the model. For this reason, when the connector of the RFID reader / writer is directly inserted into the USB terminal of the personal computer, the orientation of the RFID reader / writer case is not always determined in a certain direction. Therefore, it is desirable to ensure a long communication distance not only on the upper surface of the case but also on the side surfaces.

  However, for example, as shown in FIG. 12, when the RFID card 40 is placed perpendicular to the resonant antenna coil 23, the magnetic field in the direction entering the antenna coil 41 of the RFID card 40 and the magnetic field in the exit direction are offset, The induced voltage generated in the coil is reduced. For this reason, sufficient power for operating the IC is not supplied to the RFID card, and communication in this direction becomes difficult.

  The present invention has been proposed to solve the above-described problems of the prior art, and its purpose is to be provided in a small case and in a different direction even if the transmission / reception antenna has a small diameter. It is to provide a booster antenna capable of expanding the communication distance and communication range.

  To achieve the above object, the present invention accommodates a transmission / reception antenna for transmitting / receiving information to / from the outside, a control unit for processing information transmitted / received via the transmission / reception antenna, and the transmission / reception antenna and the control unit. A resonance antenna having a diameter larger than that of the transmission / reception antenna, and a magnetic member is disposed between the transmission / reception antenna and the resonance antenna. .

  In the invention as described above, even when a resonance antenna is provided in the case to reduce the size, the magnetic member is disposed between the transmission / reception antenna and the resonance antenna, so that the case is used for a control unit or the like. The influence of metal parts can be reduced, and the communication distance can be extended. In addition, the magnetic member allows the magnetic field generated from the resonant antenna to pass through the magnetic member and have directivity in the direction parallel to the resonant antenna, so that the communication direction increases and the communicable range is expanded.

In another aspect, the resonant antenna is a loop coil disposed on the magnetic member and attached to the inner surface of the case.
In the above aspect, since the resonant antenna and the magnetic member can be formed thin, it is easy to reduce the size.

In another aspect, the resonant antenna is embedded in the case.
In the above aspect, the space for the resonant antenna is not required in the case, so that the size can be further reduced.

In another aspect, the magnetic member includes at least one soft magnetic material of amorphous alloy, permalloy, silicon steel, sendust alloy, and soft magnetic ferrite.
In the above aspect, the influence of a metal component can be prevented by selecting an optimal magnetic member.

  According to the present invention as described above, it is possible to provide a booster antenna that is provided in a small case and can increase the communication distance and communication range in different directions even if the transmission / reception antenna has a small diameter. it can.

[Configuration of the embodiment]
Hereinafter, embodiments of the present invention will be specifically described with reference to FIGS. 1 and 2. That is, as shown in FIG. 1, the booster antenna of this embodiment is applied to an RFID reader / writer. This RFID reader / writer is configured by arranging components necessary for the reader / writer on a substrate 10 and accommodating them in a case 20. The board 10 is a substantially rectangular parallelepiped printed wiring board, and a connector 11 is provided at one end in the longitudinal direction.

  The connector 11 is a USB (Universal Serial Bus) interface capable of realizing plug and play or the like by being inserted into a connector such as a personal computer. However, the present invention is applicable to any interface that can be used now or in the future.

  In general, the male side and the female side are collectively referred to as a “connector”, and the male side is referred to as a “plug”. However, in the claims and the following description, for convenience, the “plug” is also referred to as a “connector”. Call it. The connector 11 is exposed from one end of the case 20 and is protected by a cap (not shown) that is detachable from the case 20.

  A transmitting / receiving antenna 12 is formed in a coiled pattern on the upper surface of the substrate 10 (the upper surface when connected to a personal computer). The transmission / reception antenna 12 is disposed in the vicinity of the end of the substrate 10 opposite to the connector 11.

  The substrate 10 includes a control circuit including a resonator 13, a control IC 14 and the like, and a radio wave interface. The oscillator 13 is a crystal oscillator that generates a high-frequency wave that is a carrier wave, is amplified by an amplifier, and is supplied to the transmission / reception antenna 12. It is arranged.

  The control IC 14 is a mold-sealed IC chip, and constitutes a CPU, a memory, and the like that perform processing necessary for USB connection and a reader / writer. The control IC 14 is disposed between the connector 11 and the transmission / reception antenna 12 on the lower surface side of the substrate 10.

  A resonance antenna 21, which is a circuit that is electrically independent from the circuit of the RFID reader / writer, is provided on the inner surface of the case 20. In the present embodiment, the resonance antenna 21 is disposed on the inner surface of the substrate 10 facing the transmission / reception antenna 12. Thereby, the resonant antenna 21 comes between the transmission / reception antenna 12 and the RFID card 40 when the RFID card 40 is brought closer.

  As shown in FIG. 2, the resonant antenna 21 includes a resonant antenna coil 23 wound in a loop on the magnetic member 22 and a capacitor 24 connected to the resonant antenna coil 23. It is fixed to the case 20 by being attached to the inner surface of the case 20.

  Thereby, the magnetic member 22 is disposed between the resonant antenna coil 23 and the transmitting / receiving antenna 12. Further, by arranging the resonance antenna coil 23 on the sheet-like magnetic member 22 and attaching it to the case 20, the required space can be reduced as much as possible and the miniaturization can be realized. Note that the coil length and capacitance of the resonant antenna coil 23 and the capacitor 24 are determined so as to resonate at the carrier frequency of the RFID reader / writer.

[Effects of Embodiment]
The operational effects of the present embodiment as described above will be described based on a plurality of actually produced examples and comparative examples.

[Improvement of influence of metal parts ... Examples 1 to 3]
First, the data of the result of having measured the communication distance about Comparative Examples 1-5 and Examples 1-3 which applied this embodiment are shown in the graph of Table 1 and FIG. Table 1 shows the conditions for creating the resonant antenna coil 23 and the communication distance, and FIG. 3 shows the relationship between the area ratio and the communication distance.

In Table 1, Comparative Examples 1 to 5 (items A to E) use five types of resonant antenna coils 23 having no magnetic member 22 and different areas. Examples 1 to 3 (items F to H) are obtained by changing the area of the resonant antenna coil 23 and the size of the magnetic member 22. In FIG. 3, the area ratio was determined as follows.

Area ratio = (Resonant antenna coil area) / (Transmission / reception antenna coil area)

Other conditions are as follows.
(Resonant antenna coil)
・ Resonance frequency: 13.56 MHz
-Coupling coefficient with transmission / reception antenna coil: 0.086
(Transmitting / receiving antenna coil)
・ Inductance L: 0.72μH
・ Number of windings: 7T (7 rolls)
・ Antenna radius: 3.5mm circle (magnetic member)
・ Soft magnetic ferrite rubber sheet: 500 μm thick

  As is apparent from Table 1 and FIG. 3, when Comparative Example 3 and Example 1 having the same conditions except for the presence or absence of the magnetic member 22 are compared with Comparative Example 4 and Example 2, and Comparative Example 5 and Example 3, respectively, In the embodiment, the communication distance is longer. Therefore, it can be seen that the effect of extending the communication distance by providing the resonant antenna 21 is further enhanced by interposing the magnetic member 22.

  Further, as is clear from Comparative Examples 1 to 5, if the area of the resonant antenna coil 23 is increased, the communication distance can be extended, but the area ratio becomes 10 or more and the saturated state is reached (see Comparative Examples 4 and 5). This is because the circuit pattern of the substrate 10 and the parts using the metal disposed on the substrate 10 (the lead of the control IC 14, the oscillator 13, the connector 11, etc.) exist just below the resonant antenna coil 23. It is considered that the communication distance cannot be sufficiently extended due to the influence of these metals.

  On the other hand, in Examples 2 and 3, which have the same conditions as Comparative Examples 4 and 5 except for the presence or absence of the magnetic member 22, the communication distance is greatly increased. This is considered to be because the influence of the metal can be reduced by interposing the magnetic member 22.

[Improvement of antenna coil directivity ... Embodiment 3]
Table 2 and the graph of FIG. 4 show data obtained as a result of measuring the communication distance at different positions for the above Comparative Example 5 and Example 3. Here, the different positions are the following positions A and B, which are illustrated in FIGS.
Position A (see FIGS. 5 and 6): RFID card and resonant antenna coil are positioned coaxially (communication from case upper surface 20a)
Position B (see FIGS. 5 and 7): RFID card and resonant antenna coil are positioned vertically (communication from case side surface 20b)

  As is clear from Table 2 and FIG. 4, in Comparative Example 5 where the magnetic member 22 is not present, the communication distance at the position B is significantly reduced. However, in Example 3, the communication distance at the position B is significantly longer than that of the comparative example 5 due to the magnetic member 22 being interposed, and the difference from the position A is also reduced.

  The reason why such an effect is obtained is considered to be based on the following principle. That is, in the third embodiment, as shown in FIG. 8, when the magnetic member 22 is disposed below the resonant antenna coil 23, the magnetic field generated from the resonant antenna coil 23 passes through the magnetic member 22. Directivity can be imparted in a direction parallel to the coil 23 (in-plane direction of the coil).

  Therefore, even when the RFID card 40 is placed in a direction perpendicular to the resonant antenna 21, the magnetic field penetrating the antenna coil 41 of the RFID card 40 can be increased, and the coupling coefficient between the resonant antenna coil 23 and the antenna coil 41 can be increased. It becomes possible to increase the communication distance.

[Other Embodiments]
The present invention is not limited to the above-described embodiment, and includes other embodiments as follows.

となる。この場合、インダクタンスＬとキャパシタンスＣの値の調整で、共振周波数を変更できるが、搬送周波数に対して多少高い周波数にした方が値のばらつきに対して余裕がでる。 (a) When the resonance point wave of the resonance antenna 21, the resonance frequency is f, the inductance is L, and the capacitance is C,

It becomes. In this case, the resonance frequency can be changed by adjusting the values of the inductance L and the capacitance C. However, if the frequency is slightly higher than the carrier frequency, there is a margin for variation in the values.

  In addition, the specific numerical value in each embodiment is an illustration, and this invention is not limited to said numerical value. A specific example of the carrier frequency is 13.56 MHz, but is not limited thereto.

(b) In order to increase the effect of the resonant antenna 21, adjustment is performed to match the impedance of the resonant circuit of the transmitting / receiving antenna 12 formed on the substrate with the output impedance of the RF section. By adjusting with an LCR meter or the like, the peak of the resonance frequency is made lower than the carrier frequency.

(c) The effect of the present invention is not achieved unless the transmitting / receiving antenna 12 on the substrate is within the loop of the resonant antenna coil 23 when viewed from above the substrate. However, in consideration of this point, the positional relationship between the transmission / reception antenna 12 and the resonance antenna 21 is not limited to the illustrated one. For example, the two antenna coils do not necessarily have to be parallel to each other, and the axes need not coincide. Moreover, the shape of both antenna coils may be circular, elliptical, square, or other shapes.

(d) The circuit on the resonance antenna 21 side can be formed on an adhesive sheet by using a printing technique, or can be formed on a flexible substrate by printing or the like, and can be manufactured thinly and inexpensively.

(e) As shown in FIG. 9, the resonant antenna coil 23 can be embedded in the resin constituting the case 20. With this configuration, the space of the thickness of the resonant antenna coil 23 inside the case 20 can be saved, so that further downsizing is possible.

(f) The distance between the transmission / reception antenna 12 on the substrate and the resonance antenna 21 is the same as the radius of the antenna on the substrate, and the communication distance is the largest, but within this distance, the resonance antenna 21 is not used. The effect can be confirmed compared to. However, when the resonance antenna 21 is used at a distance greater than the radius, the effect is not always sufficient.

(g) The position where the resonance antenna 21 is provided on the case 20 may be on either the upper surface side or the lower surface side of the case 20 in consideration of the positional relationship with the transmission / reception antenna 12 as described above. In addition, as long as the area of the resonant antenna 21 can be accommodated in the case 20, it is more effective to maximize the area.

(h) The magnetic member 22 is preferably made of a soft magnetic material such as amorphous alloy, permalloy, silicon steel, sendust alloy, soft magnetic ferrite, but is not limited thereto. The magnetic material may be one kind or plural kinds, and may include a nonmagnetic material.

It is sectional drawing which shows the structure of one Embodiment of this invention. It is a top view which shows the resonant antenna in embodiment of FIG. It is explanatory drawing which shows the relationship between the resonance antenna coil area and communication distance in embodiment of FIG. It is explanatory drawing which shows the comparison of the communication distance of Example 3 and Comparative Example 5 in embodiment of FIG. It is explanatory drawing which shows communication with the RFID card | curd in the different positions A and B in embodiment of FIG. It is a perspective view which shows the state of the position A of FIG. It is a perspective view which shows the state of the position B of FIG. It is explanatory drawing which shows the magnetic field in the position B of embodiment of FIG. It is sectional drawing which shows other embodiment of this invention. It is sectional drawing which shows the RFID reader / writer which provided the conventional resonant antenna in the case. It is sectional drawing which shows the RFID reader / writer which embedded the conventional resonant antenna in the case. It is explanatory drawing which shows the magnetic field in communication with the conventional RFID reader / writer and RFID card.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Board | substrate 11 ... Connector 12 ... Transmitting / receiving antenna 13 ... Oscillator 20 ... Case 21 ... Resonant antenna 22 ... Magnetic member 23 ... Resonant antenna coil 24 ... Capacitor 40 ... Card 41 ... Antenna coil

Claims (4)

A transmission / reception antenna for transmitting / receiving information to / from the outside, a control unit for processing information transmitted / received via the transmission / reception antenna, and a case housing the transmission / reception antenna and the control unit,
The case is provided with a resonant antenna having a larger diameter than the transmitting / receiving antenna,
A booster antenna, wherein a magnetic member is disposed between the transmission / reception antenna and the resonance antenna.   The booster antenna according to claim 1, wherein the resonant antenna is a loop coil disposed on the magnetic member and attached to the inner surface of the case.   The booster antenna according to claim 1, wherein the resonant antenna is embedded in the case.   The booster antenna according to any one of claims 1 to 3, wherein the magnetic member includes at least one kind of soft magnetic material among amorphous alloy, permalloy, silicon steel, sendust alloy, and soft magnetic ferrite. .

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