JP2009253797A - Wireless communication device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thin and inexpensive wireless communication device in which influence of eddy current generated by an input magnetic field is suppressed. <P>SOLUTION: A wireless communication device 1 for performing data communication in a non-contact manner includes an IC chip 2, an antenna pattern 4, and a capacitor 5 for frequency adjustment therein. A slit 6 is formed from an outer peripheral region toward an inside on a conductor film forming the capacitor 5 for frequency adjustment. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention is used for an RF-ID (Radio Frequency Identification) or NFC (Near Field Communication), that is, a wireless communication medium processing apparatus that performs communication with a wireless communication medium such as an IC card or an IC tag, or the wireless communication medium itself. The present invention relates to a wireless communication device, which relates to an electromagnetic induction method and a microwave method, and relates to a thin and low-cost wireless communication device.

As a tag using the RFID technology, a contactless tag in which an IC chip storing information is electrically connected to an antenna coil is known. These non-contact tags activate the IC chip in the tag by transmitting radio waves of a predetermined frequency from the IC card reader / writer to the antenna coil, and information stored in the IC chip in response to a command from the reader / writer The tag can be identified by reading. As an antenna coil used for such a non-contact type tag or reader / writer, a loop antenna is mainly used. A conductive magnetic material is arranged to extend the communication distance, and an eddy current generated in the magnetic material is reduced. In order to prevent this, a slit is provided (see, for example, Patent Document 1).
JP 2007-110290 A

  However, in the case of an IC tag that uses an IC chip that consumes a large amount of power, the input impedance of the IC chip is small, so the impedance of the antenna coil must also be reduced. Must be set small. However, when trying to resonate a low-inductance circuit, a large-capacity capacitance must be electrically connected to the inductance. In the conventional configuration, there is a problem that the antenna coil cannot be electrically connected to the capacitor. Even if the magnetic material is replaced with a capacitor, the slit is provided to the center of the conductive magnetic material, so the capacity of the capacitor corresponding to the slit is reduced and the required large capacity capacitor is realized. It was difficult to do.

  Therefore, in view of the above-described conventional problems, the present invention provides wireless communication that can suppress generation of a demagnetizing field due to eddy current while configuring a large-capacity capacitance for resonating a low-inductance circuit in the wireless communication device. An object is to provide an apparatus.

  In order to solve the above problems, the present invention is a wireless communication apparatus that performs data communication without contact, and is a wireless communication apparatus having an LSI, an antenna pattern, and a frequency adjustment capacitor in the wireless communication apparatus, A slit is formed only in the outer peripheral portion toward the inner side of the conductor film forming the frequency adjusting capacitor.

  According to the configuration of the present invention, it is possible to provide a wireless communication apparatus that can suppress generation of a demagnetizing field due to eddy current while configuring a large capacity capacitance for resonating a low inductance circuit in the wireless communication apparatus. it can.

  The invention according to claim 1 of the present invention is a wireless communication apparatus that performs data communication without contact, and is a wireless communication apparatus having an LSI, an antenna pattern, and a frequency adjusting capacitor in the wireless communication apparatus, A wireless communication device characterized in that a slit is formed only in the outer peripheral portion toward the inside of the conductor film forming the adjustment capacitor, and the slit is formed in the conductor film forming the frequency adjustment capacitor. The eddy current path is divided into a plurality of sections, and the eddy currents facing each other across the slit cancel each other's generated magnetic field, and the sum of the canceling magnetic fields due to the eddy current can be suppressed. Further, by suppressing the slit length, the total amount of the canceling magnetic field due to the eddy current can be suppressed while suppressing the amount of the conductive film forming the frequency adjusting capacitor reduced by the slit.

  The invention according to claim 2 of the present invention is the wireless communication device according to claim 1, wherein the antenna pattern and the frequency adjusting capacitor are formed of a conductor film and have a laminated structure. Capacitance can be greatly increased by forming the film in a laminated structure.

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

  FIG. 1 is a perspective view of a wireless communication apparatus 1 according to an embodiment of the present invention.

  In the wireless communication device 1 shown in FIG. 1, an antenna pattern 4 is formed on a substrate 3 and is electrically connected to the IC chip 2. In addition, a frequency adjusting capacitor 5 is formed in a portion of each layer of the substrate 3 corresponding to the lower portion of the IC chip 2. A plurality of slits 6 are formed in the conductive film forming the frequency adjusting capacitor 5 from the outer periphery to the inner side of the conductive film.

  Hereinafter, the configuration of the wireless communication device 1 will be described.

  First, the substrate 3 will be described. The substrate 3 is a base substrate on which electronic members such as the IC chip 2, the antenna pattern 4, and the frequency adjusting capacitor 5 are mounted. In this embodiment, any substrate may be used as long as it has insulating properties, for example, polyimide, It can be formed of PET, glass epoxy substrate or the like.

  Next, the antenna pattern 4 will be described. The antenna pattern 4 is formed in a spiral shape. The spiral structure may be a spiral shape having an opening at the center, and the shape may be a circle, a substantially rectangle, or a polygon represented by a triangle or a rectangle. By adopting a spiral structure, it is possible to read information stored in the IC chip by linking the magnetic field generated from the reader / writer to the opening, inducing induced power, and activating the IC chip. Communication with the reader / writer becomes possible. Further, the pattern material may be any conductive material such as gold, silver, copper, aluminum, nickel or other conductive metal wire, metal plate, metal foil, or metal cylinder. It can select suitably from etc., and can form by metal wire, metal foil, an electrically conductive paste, plating transcription | transfer, sputtering, vapor deposition, or screen printing.

  Next, the frequency adjusting capacitor 5 will be described. The frequency adjusting capacitor 5 is formed inside the antenna pattern 4. The material of the conductor film can be appropriately selected from conductive metal wire materials such as gold, silver, copper, aluminum, nickel, metal plate materials, metal foil materials, metal tube materials, etc. It can be formed by metal foil, conductive paste, plating transfer, sputtering, vapor deposition, or screen printing.

  Further, although the shape of the frequency adjusting capacitor 5 will be described later, it may be a polygonal shape such as a triangular shape or a quadrangular shape or a circular shape. In order to increase the capacitance of the capacitor as much as possible, the inner periphery of the antenna pattern 4 may be used. A shape close to this shape is preferable because there is little wasted space when it is placed.

  Next, the slit 6 will be described. The slit 6 is formed from the outer periphery to the inner side of the conductive film forming the frequency adjusting capacitor 5. The slit 6 can be formed by pattern etching or the like.

  Next, the structure of the wireless communication apparatus of the present invention will be described in detail with reference to FIG. 2 and FIG. FIG. 2 is a copper foil pattern diagram of each layer of the substrate in the embodiment of the present invention, and FIG. 3 is a circuit diagram in the embodiment of the present invention.

  The substrate 3 is made of a glass-epoxy substrate, and as shown in FIGS. 2A to 2B, each layer of the substrate 3 includes an antenna pattern 4 for one turn and a capacitor 5 for frequency adjustment. The frequency adjusting capacitor 5 is formed at the center of the substrate 3, and a slit 6 is provided on the outer periphery thereof. An antenna pattern is formed so as to surround the frequency adjusting capacitor 5.

  The antenna pattern 4 and the frequency adjusting capacitor 5 are formed by performing pattern etching on two glass epoxy substrates of double-sided copper foil, and bonding the glass epoxy substrate with glass epoxy resin. Via a and Via a ′, Via b and Via b ′, Via c and Via c ′, Via d and Via d ′ and Via d ″, Via e and Via e ′ and Via e ″ are IVH or The layers are electrically connected and stacked by through holes.

  The wireless communication device 1 described above has a circuit diagram as shown in FIG. 3, and two antenna terminals provided in the IC, L and C are electrically connected in parallel, and are configured by a parallel resonance circuit. Yes. In the embodiment of the present invention, the IC in FIG. 3 corresponds to the IC chip 2, L corresponds to the antenna pattern 4, and C corresponds to the frequency adjustment capacitor 5. The circuit may be a series resonance circuit instead of a parallel resonance circuit.

  The slit 6 is formed by performing pattern etching from the outer periphery to the inner side of the conductive film forming the frequency adjusting capacitor 5. The frequency adjusting capacitor 5 generates a demagnetizing field due to an eddy current generated by a magnetic field in the normal direction, leading to a decrease in communication performance. However, as shown in FIG. The generation of a demagnetizing field can be suppressed by the eddy currents that flow oppositely cancel each other's induction magnetic field. FIG. 5 is a diagram showing the magnetic field strength generated on the surface of the square frequency adjustment capacitor in the embodiment of the present invention. Since the eddy current flowing on the surface of the conductive film is proportional to the magnetic field strength generated on the surface of the conductive film, the magnetic field strength in FIG. 5 may be replaced with the strength of the eddy current. As shown in FIG. 5, almost no eddy current flows near the center of the frequency adjusting capacitor 5, and the eddy current is concentrated near the outer periphery. Therefore, the slit is formed only in the portion where the eddy current is concentrated. What is necessary is that the length of the slit can be greatly reduced.

  For example, in order to suppress the strength of the canceling magnetic field to 10%, the length of the slit 6 may be about 1 mm from the outer periphery to the inner side of the conductive film. That is, since the slit 6 is provided from the outer peripheral portion where the decrease of the eddy current is large, the amount of the conductor film reduced by the slit 6 can be suppressed, and the capacitance is maintained while suppressing the generation of the demagnetizing field due to the eddy current. It becomes possible to do.

  That is, in order to suppress the eddy current while suppressing the decrease in the capacitor capacity of the frequency adjusting capacitor 5 which is a conductor film, the outer periphery where a large amount of eddy current flows is not provided in the inside where the eddy current does not flow so much. It is necessary to provide the slit 6 only in the portion.

  Hereinafter, the shape of the frequency adjusting capacitor 5 will be described. First, the case where the frequency adjusting capacitor 5 is square will be described.

  The frequency adjusting capacitor 5 has a square shape as shown in FIG. A magnetic field is generated on the surface of the frequency adjusting capacitor 5 in a direction perpendicular to the surface of the frequency adjusting capacitor 5 by an eddy current induced by the interlinkage magnetic flux as shown in FIG. As shown in FIG. 5, the intensity of the magnetic field generated by the eddy current is strongest at the edge of the frequency adjusting capacitor 5 and sharply decreases toward the center. When the slit 6 is formed inward from the outer peripheral portion of the frequency adjusting capacitor 5, the eddy current path becomes along the slit 6 as shown in FIG. The induced magnetic fields generated by the currents cancel each other. That is, the path of the eddy current flowing in the portion corresponding to the length from the outer periphery of the slit 6 is along the slit 6, and the induced magnetic fields generated by the eddy current are canceled each other. When the frequency adjusting capacitor 5 is square, the 4-turn antenna pattern 4 and the frequency adjusting capacitor 5 are formed on the substrate 3 and the inner layer of the substrate 3, and the outer dimension is 9 mm and the inner dimension is 8 mm. It consists of an antenna pattern 4 and a frequency adjusting capacitor 5 having one side of 7 mm. Further, in order to suppress the maximum magnetic field strength to 10%, the length of the slit 6 is set to 0.7 mm as shown in FIG.

  When the strength of the canceling magnetic field needs to be suppressed to 10% as described above, the slit 6 may be provided by about 0.7 mm. However, as shown in FIG. Since the eddy current is greatly reduced up to about 0.5 mm, considering the decrease in the capacity of the frequency adjusting capacitor 5 due to the provision of the slit 6, the slit 6 is formed about 0.5 mm from the outer periphery to the inside of the conductive film. It is preferable to provide it.

  Next, the case where the frequency adjusting capacitor 5 is a regular decagon as shown in FIG. 7 will be described. Even in the case where the frequency adjusting capacitor 5 is a regular decagon, the induction magnetic field caused by the eddy current is suppressed by forming the slit 6 inward from the outer periphery of the frequency adjusting capacitor 5 as in the case of the square. can do. In the case of a regular decagon, a 4-turn antenna pattern 4 and a frequency adjusting capacitor 5 are formed on the substrate 3 and the inner layer of the substrate 3, and the antenna pattern 4 has an outer dimension of 9 mm and an inner dimension of 8 mm. And the frequency adjusting capacitor 5 having an outer dimension of 7 mm. Further, in order to suppress the maximum magnetic field strength to 10%, the length of the slit 6 is set to 1 mm as shown in FIG.

  In consideration of the decrease in the capacitance of the frequency adjusting capacitor 5 due to the provision of the slit 6, it is preferable to provide the slit 6 about 0.4 mm from the outer periphery to the inner side of the conductive film. Thus, when the maximum magnetic field strength is suppressed to 10%, it may be 1.0 mm.

  Next, the case where the frequency adjusting capacitor 5 is rectangular as shown in FIG. 9 will be described. Even when the frequency adjusting capacitor 5 is rectangular, by forming the slit 6 from the outer periphery of the frequency adjusting capacitor 5 toward the inside, it is possible to suppress an induced magnetic field due to eddy current. In the case of a rectangle, a 4-turn antenna pattern 4 and a frequency adjusting capacitor 5 are formed on the substrate 3 and the inner layer of the substrate 3, and the antenna pattern has an outer dimension of 13 mm × 5 mm and an inner dimension of 12 mm × 4 mm. 4 and a frequency adjusting capacitor 5 having an outer dimension of 11 mm × 3 mm. Further, in order to suppress the maximum magnetic field strength to 10%, the length of the slit 6 is set to 0.6 mm as shown in FIG.

  In consideration of a decrease in the capacitance of the frequency adjusting capacitor 5 due to the provision of the slit 6, it is preferable to provide the slit 6 about 0.3 mm from the outer periphery to the inner side of the conductive film.

  As described above, the present invention sets the slit length necessary for suppressing the maximum intensity of the canceling magnetic field to 10%, but the slit length is not limited to 10% and is suitable for the amount to be suppressed. The length may be set.

  That is, the length that can obtain the optimum efficiency of the reduction of the eddy current due to the slit 6 and the reduction of the capacitance of the frequency adjustment capacitor 5 differs depending on the shape as described above. It may be selected as appropriate in consideration of the maximum strength of the canceling magnetic field.

  As shown in FIG. 11, the slit 6 formed in the frequency adjusting capacitor 5 is not only shaped from the four directions of the outer peripheral portion of the frequency adjusting capacitor 5 toward the center, but also shown in FIG. 12, for example. Thus, the shape from the other direction toward the center may be used. Further, the slit 6 does not have to have a shape from the outer peripheral portion of the frequency adjusting capacitor 5 toward the center. For example, as shown in FIG.

  The slit 6 is rectangular in the above embodiment, but may be other shapes such as a triangle. However, the parallel frequency adjusting capacitor 5 facing the slit 6 is more effective in canceling eddy currents. It is preferable because it is the highest.

  When the gap between the frequency adjusting capacitor 5 and the antenna pattern 4 is set wide, the interlinkage magnetic flux passing through the frequency adjusting capacitor 5 is reduced. That is, since the eddy current flowing on the surface of the frequency adjusting capacitor 5 becomes small, the length of the slit may be small. Further, when the gap between the frequency adjusting capacitor 5 and the antenna pattern 4 is set to be narrow, the flux linkage of the antenna pattern 4 becomes small, leading to deterioration of communication characteristics. A necessary minimum gap is required between the frequency adjusting capacitor 5 and the antenna pattern 4. In the embodiment of the present invention, the gap between the frequency adjusting capacitor 5 and the antenna pattern 4 is set to 0.5 mm.

  As described above, according to the present invention, it is possible to suppress the influence of eddy currents while relatively suppressing the decrease in the capacitance of the capacitor.

  5, 8, and 10 show the case where the frequency is 13.56 MHz. When the frequency is higher than this, the eddy current of the frequency adjusting capacitor 5 is collected on the outer peripheral side, so that the slit 6 is compared with the above case. When the frequency is lower than 13.56 MHz, the eddy current of the frequency adjusting capacitor 5 is dispersed also in the inner periphery, so that it is necessary to lengthen the slit 6.

  Further, in the plurality of laminated frequency adjusting capacitors 5, it is preferable that the slits 6 are provided at the same position and in the same shape and the capacitance can be increased as a capacitor.

  The wireless communication device of the present invention is useful for a wireless communication device such as a small antenna device having a low inductance circuit.

The perspective view of the radio | wireless communication apparatus in the Example of this invention Copper foil pattern diagram of each layer of the substrate in the embodiment of the present invention 1 is a circuit diagram of a wireless communication apparatus according to an embodiment of the present invention. The top view explaining the state which an eddy current generate | occur | produces in the capacitor for frequency adjustment of this invention The figure showing the magnetic field intensity which generate | occur | produces on the capacitor surface for square frequency adjustment in the Example of this invention The top view which shows the antenna pattern in Example 1 of this invention, and the square frequency adjustment capacitor The top view which shows the capacitor for frequency adjustment of the regular decagon in the Example of this invention The figure showing the magnetic field intensity which generate | occur | produces on the capacitor surface for regular decagonal frequency adjustment in the Example of this invention The top view which shows the rectangular capacitor for a frequency adjustment in the Example of this invention The figure showing the magnetic field intensity which generate | occur | produces on the surface of the rectangular frequency adjustment capacitor in the Example of this invention The top view which shows the slit in the Example of this invention The top view which shows the other slit in the other Example of this invention. The top view which shows the other slit in the other Example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Wireless communication apparatus 2 IC chip 3 Board | substrate 4 Antenna pattern 5 Capacitor for frequency adjustment 6 Slit

Claims (2)

A wireless communication device that performs non-contact data communication, wherein the wireless communication device includes an LSI, an antenna pattern, and a frequency adjustment capacitor in the wireless communication device, and the inside of the conductor film that forms the frequency adjustment capacitor A wireless communication device characterized in that a slit is formed only in the outer peripheral portion toward the surface. The radio communication apparatus according to claim 1, wherein the antenna pattern and the frequency adjusting capacitor are formed of a conductor film and have a laminated structure.

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