JP4779417B2 - Non-contact IC card reader / writer - Google Patents

Description

  The present invention relates to a non-contact IC card reader / writer, and more particularly to an electromagnetic shield structure of an antenna portion thereof.

As is well known, a non-contact IC card reader / writer supplies power to an IC card by electromagnetic induction together with transmission (reading / writing) of a data signal with a non-contact IC card (data carrier) such as electronic money. This is a terminal device that has a sheet antenna board and RF board (printed board with an RF signal processing circuit) with a loop antenna pattern formed on the board mounted on the main body case. Has a configuration in which a card touch area is formed to touch or hold a contactless IC card or a mobile phone with a built-in RFID tag facing the antenna board.
Non-contact IC card readers / writers are classified into close contact type, proximity type, proximity type, and the like according to the communication distance with the IC card, and are of proximity type and proximity type using an IC card such as electronic money as a data carrier. In the RFID system, the carrier frequency band is defined as 13.56 MHz in the international standard. In addition, there are mobile types, stationary types, wall-mounted types, etc., depending on the type of use, and more recently, development of products to be used in vending machines is also underway.

An assembly manufacturer that manufactures and sells the above non-contact IC card reader / writer purchases an embedded RF module with an antenna board and RF board from a specialized manufacturer and makes it according to the usage of the product. After assembling the module into the case, the product is assembled by additionally providing a display for displaying information as necessary.
By the way, in order to make the above-mentioned card reader / writer product compact, a configuration in which an antenna board is arranged in the case facing the card touch area formed on the front surface of the main body case, and an RF board is arranged behind the antenna board. However, in such a mounting structure, unnecessary electromagnetic interference occurs between the antenna board and the RF board in use, and the case housing is made of sheet metal or mounted on a vending machine. In addition, if there is a metal structure (such as a table or wall where the card reader / writer is installed) around the place where the card reader / writer is used, the antenna board will be affected by electromagnetic induction due to these metal objects. It becomes like this. For this reason, the coil characteristics of the antenna (the resonance frequency of the coil adjusted at the time of shipment from the manufacturer in accordance with the specified carrier frequency) change, and as a result, the communication distance of the card reader / writer is extremely reduced. There may be a problem that communication with the IC card cannot be normally performed.

In addition, the RF board provided by the parts manufacturer is equipped with a variable capacitor that can be adjusted in the oscillation circuit of the antenna coil as a means for adjusting the coil characteristics, so that the resonance of the coil can also be achieved on the user side (card reader / writer assembly manufacturer). The frequency can be adjusted. However, when the card reader / writer is assembled, re-adjusting the coil characteristics of the RF module according to the usage pattern of the product requires labor and time for the adjustment work, and requires a dedicated adjustment tool. There is a problem. Therefore, an assembler of a card reader / writer needs to take measures against EMI (unwanted radiation) in order to assemble a purchased RF module without adjustment and to exhibit a stable communication function.
On the other hand, various electromagnetic shielding materials have recently been developed and commercialized as EMI countermeasures applied to electronic devices (see, for example, Non-Patent Document 1), and the contactless IC card reader / writer is also behind the antenna board. A plate-like high-permeability ferrite material is arranged, or a sheet-like electromagnetic shielding material disclosed in Non-Patent Document 1 (fine particles of a high-permeability material such as ferrite are kneaded into a resin substrate to form a sheet. In some products, measures are taken to prevent unnecessary electromagnetic interference by sticking to the back of the antenna board and the inner surface of the metal casing that constitutes the main body case.
Composite electromagnetic shielding material [online], TDK Corporation, [March 2005 Search] Internet <URL: http://www.tdk.co.jp/tjbab01/bab00109.pdf>

  By the way, the sheet-like electromagnetic shielding material (trade name: Flexield IRL04 (manufactured by TDK Corporation)) introduced in the above-mentioned Non-Patent Document 1 is adopted for a non-contact IC card reader / writer having a frequency band of 13.56 MHz. In order to verify whether or not the predetermined communication function can be secured even if the RF board provided by the manufacturer is left unadjusted, the inventor of the antenna board incorporating the electromagnetic shielding material in the main body case. When the effect on the coil characteristics (resonance frequency characteristics) of the antenna by pasting it on the back surface was investigated by experiment, the effect of reducing electromagnetic interference with surrounding metal objects was obtained, but the antenna board was used as it was It was recognized that the resonance frequency of the coil changed compared to, and was lower than the default frequency band. Therefore, if the reader / writer is assembled as it is, the communication distance will decrease, and in order to secure the communication distance as specified, the RF board is again adjusted to match the coil characteristics to the predetermined appropriate frequency band. It is necessary to make it. By the way, if the electromagnetic shielding material is placed behind and separated from the antenna board, the influence of the electromagnetic shielding material on the antenna board decreases as the gap length increases, and the resonance frequency of the coil increases somewhat. On the other hand, if the distance (gap length) between the antenna board and the electromagnetic shielding material is increased, the antenna is more susceptible to the influence of surrounding metal objects and the data communication function becomes unstable. As a result, the outer space of the main body case becomes larger.

In addition, the inventor replaces the electromagnetic shielding material with a sheet metal member (thickness of about 0.8 to 1 mm) made of a normal steel plate (magnetic material) and faces the antenna board to achieve antenna characteristics. As a result of investigating the influence, it was recognized that, contrary to the electromagnetic shielding material, the resonance frequency of the antenna was affected and the resonance frequency was further increased as the sheet metal member was brought closer to the antenna board.
Therefore, the object of the present invention is to use a commercially available electromagnetic shielding material (see Non-Patent Document 1) as an EMI countermeasure based on the knowledge obtained in the above verification, and to suppress unnecessary electromagnetic interference on the antenna board. It is an object of the present invention to provide a non-contact IC card reader / writer with an improved electromagnetic shield structure of an antenna board that can be assembled as it is without re-adjusting the antenna coil characteristics of an RF module purchased from, and can exhibit a predetermined communication performance.

To achieve the above object, according to the present invention, a non-contact IC card reader / writer which communicates data signals to and from the contactless IC card, and this to the antenna board and behind in the body case In a configuration in which an RF board for signal processing forming an embedded RF module in a set is arranged,
Behind the antenna board, a sheet-like electromagnetic shielding material having an electromagnetic wave absorbing function is placed opposite to the back surface of a magnetic sheet metal member, and the electromagnetic shielding material is arranged with a predetermined gap from the antenna board. it allows a structure in which Ru is matched to the resonant frequency of the antenna of the RF module arranged in said body in a predetermined frequency band.

Compared to the case where the electromagnetic shielding material is used alone, the magnetic sheet metal member is overlapped on the sheet-shaped electromagnetic shielding material having an electromagnetic wave absorption function and arranged oppositely behind the antenna board as in the above configuration. The resonance frequency of the coil shifts in the direction of increasing. As described in the above-mentioned verification, the electromagnetic shield material and the sheet metal member have opposite directions in which the resonance frequency of the coil is changed by affecting the antenna board, and by combining the sheet metal material on the back surface of the electromagnetic shield material, , Electromagnetic waves that have passed through the electromagnetic shield member (the sheet-like electromagnetic shield material alone cannot completely absorb the electromagnetic waves) are affected by the sheet metal member superimposed on the back surface, and the resonance frequency of the coil is increased. It is because it comes to do.
Therefore, when assembling the card reader / writer, the magnetic sheet metal member is superimposed on the back surface of the electromagnetic shielding material as described above, and the distance (gap length) is set appropriately by approaching the back of the antenna board. Thus, the antenna coil characteristics are matched to the band of 13.2 to 13.4 MHz, for example, by matching the carrier frequency band of the appropriate frequency to the standard (13.56 MHz) described above, and the shield by the electromagnetic shielding material and the sheet metal member. Due to the effect, electromagnetic interference with the RF board disposed behind the antenna board and surrounding metal objects can be reduced, and a predetermined communication distance can be secured. As a result, it is possible to manufacture a non-contact IC card reader / writer having a compact design corresponding to various usage forms by assembling an RF module purchased from a manufacturer without adjustment.

Hereinafter, embodiments of the present invention will be described based on the illustrated examples.
First, taking a stationary card reader / writer as an example, an assembly structure according to an embodiment of the present invention is shown in FIGS. 1 (a), 1 (b) and FIG. In each figure, 1 is a main body case of a two-part structure comprising a lower case 1a and an upper cover 1b, 2 is an antenna board installed inside the case facing the card touch area 1c formed on the surface of the upper cover 1b, 3 Is an RF board for signal processing that is arranged behind the antenna board 2 and incorporated in the lower case 1a, 4 is a sheet-like electromagnetic shield material arranged behind the antenna board 2 as an EMI countermeasure, and 5 is on the back surface of the electromagnetic shield material A magnetic sheet metal member bonded together, and the electromagnetic shielding material 4 carried on the sheet metal member 5 is opposed to the antenna board 2 with a predetermined gap length L (details will be described later on the setting of the gap length L). Has been placed. Reference numeral 1d denotes a display panel arranged on the upper side of the card touch area 1c and mounted on the upper cover 1b.

Here, the detailed structure of the electromagnetic shielding material 4 and the sheet metal member 5 is shown in FIGS. First, the electromagnetic shielding material 4 employs the electromagnetic shielding material (trade name: Flexield IRL04 (manufactured by TDK Corporation)) introduced in the above-mentioned Non-Patent Document 1, and the external size (vertical Hs × horizontal Ws) is an antenna. After cutting into a size corresponding to the outer shape of the board 2, a concave groove for releasing the connector 2 a (see FIG. 2) of the antenna board 2 is formed in the periphery thereof. The sheet metal member 5 is a steel plate (magnetic material) having a thickness of about 0.8 to 1.0 mm with mounting tabs 5a formed at the four corners, and the outer size (vertical Hp × horizontal Wp) is the outer shape of the electromagnetic shielding material 4. The size is set equal to or slightly smaller than the size so that the periphery of the sheet metal member 5 does not protrude when the electromagnetic shield material 4 (adhesive is applied to the back surface of the shield material) is bonded as shown in FIG. It is set.
Next, an assembly structure in which the antenna board 2 and the composite shield body in which the electromagnetic shield material 4 and the sheet metal member 5 are bonded to each other is mounted on the upper cover 1b of the main body case 1 is shown in FIGS. 5 (a) and 5 (b). explain. That is, the antenna board 2 is inserted into the fixing hooks 1a-5 erected on the inner side of the upper cover 1b while fitting the mounting holes drilled in the four corners of the board to the support pins 1a-1. Is hooked on the fixing hook 1a-2 and fixed in place.

On the other hand, the sheet metal member 5 bonded to the electromagnetic shielding material 4 has a step on the left side of the support tabs 5a formed at the four corners, and is stepped on the left inner side of the cover 1b. The fixed hook 1a-4 is inserted into and engaged with the stepped portion of the fixed hook 1a-4, and the right hook is then hooked and fixed while the right hook is bent on the right inner side of the cover. In this assembled state, the gap length set between the antenna board 2 and the electromagnetic shielding material 4 disposed behind the antenna board 2 so as to be matched with the appropriate frequency based on the coil characteristics shown in the characteristic diagram of FIG. An interval of L is secured.
That is, FIG. 6 shows the above-mentioned electromagnetic shield behind the antenna board 2 as an EMI countermeasure for a non-contact IC card card reader / writer that uses a proper frequency in a carrier frequency band specified in a range of 13.2 to 13.4 MHz, for example. Verification of how the distance (gap length L) from the antenna board 2 affects the resonance frequency of the coil when a composite shield body in which the material 4 and the magnetic sheet metal member 5 are bonded together is disposed. FIG. 5 is a coil characteristic diagram actually measured in an experiment for the purpose of testing, in which the coil characteristics when only the electromagnetic shield material 4 is used alone and when only the sheet metal member 5 is used as a comparative example are also shown. ing.

As can be seen from this coil characteristic diagram, when only the sheet metal member 5 is used alone, the initial resonance frequency of the coil (the RF frequency purchased from the manufacturer has an antenna coil resonance frequency of 13.2 to 13). The sheet metal member affects the direction in which the resonance frequency is increased, while being adjusted to match an appropriate frequency in the range of 4 MHz). Further, when only the electromagnetic shielding material 4 is used alone, it affects the direction of lowering the resonance frequency contrary to the sheet metal member 5, and in particular, the electromagnetic shielding material 4 is disposed close to the antenna board 2 (gap length L: 10 mm). In the case of the following), the resonance frequency of the antenna coil greatly shifts to the lower side exceeding the appropriate frequency band (13.2 to 13.4 MHz).
On the other hand, in the composite shield body of the illustrated embodiment in which the magnetic sheet metal member 5 is bonded to the back surface of the electromagnetic shield material 4, the coil characteristics (resonance frequency) of the antenna are compared with the case where only the electromagnetic shield material 4 is used alone. Will shift higher. It can be seen that if the gap length L between the antenna board 2 and the electromagnetic shielding material 4 is set to 4 mm, the resonance frequency of the antenna coil can be matched to an appropriate frequency in the range of 13.2 to 13.4 MHz. When only the electromagnetic shielding material 4 is used and the gap length between the antenna board 2 and the antenna board 2 is set to 4 mm, the resonance frequency of the antenna coil is higher than the proper frequency band of 13.2 to 13.4 MHz. It will change to the lower one.

Accordingly, the support seat of the antenna board 2 provided on the upper cover 1b and the metal member so that the gap length L between the antenna board 2 and the electromagnetic shield material 4 is 4 mm in the assembly structure shown in FIG. The RF module purchased from the manufacturer is assembled by assembling the card reader / writer by assembling the antenna board 2, the electromagnetic shielding material 4 and the sheet metal member 5 by setting a step between the support seat (see FIG. 5). High reliability that can exhibit stable communication function with non-contact IC card by suppressing unnecessary electromagnetic interference with RF board and surrounding metal objects while omitting troublesome process of adjusting characteristics Product can be manufactured at low cost.
In the illustrated embodiment, the stationary card reader / writer is described. However, the present invention can be similarly applied to a card reader / writer mounted on a mobile type, a wall-hanging type, or a vending machine having a different usage pattern.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an assembly structure diagram of a card reader / writer according to an embodiment of the present invention, in which FIG. Figure 1 is an exploded perspective view of FIG. It is a block diagram of the composite shielding member which combined the electromagnetic shielding material and sheet metal member shown in FIG.1 (b), (a), (b), (c) is a top view, a side view, and a rear view, respectively. FIG. 3 is an exploded perspective view. 4A and 4B are diagrams showing a detailed internal structure of a main body case incorporating the antenna board shown in FIG. 1 and the composite shield member shown in FIG. Installation illustration of Fig. 3 shows the resonance frequency characteristics of the antenna coil, showing the effect of the composite shield member shown in Fig. 3 on the coil characteristics of the antenna in comparison with the comparative example using only the electromagnetic shield material and only the sheet metal member.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Card reader / writer main body case 1a Card touch area 2 Antenna board 3 RF board 4 Sheet-like electromagnetic shielding member 5 Magnetic sheet metal member L The space | gap length between an antenna board and an electromagnetic shielding material

Claims (1)

A non-contact IC card reader / writer that exchanges data signals with a non-contact IC card. For signal processing, an antenna board is built in the main body case and a built-in RF module in combination with the antenna board. In the configuration in which the RF board is arranged, a sheet-like electromagnetic shielding material having an electromagnetic wave absorbing function is placed behind the antenna board so as to be opposed to each other with a magnetic sheet metal member superimposed thereon, and the electromagnetic shielding material is arranged on the antenna board. A non-contact IC card reader / writer characterized in that the resonance frequency of the antenna of the RF module disposed in the main body is matched with a predetermined frequency band by disposing it at a predetermined gap .

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