BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to an antenna device and an IC card having the antenna device and, more particularly, to an antenna device including a coupling coil electromagnetically coupled to an IC module and an antenna coil electromagnetically coupled to a card reader and an IC card provided with the antenna device having such a configuration.

Description of Related Art

IC cards having an IC module have been widely used recently. For example, JP H11-149536A and JP 2008-067057A disclose an IC card including a coupling coil electromagnetically coupled to an IC module and an antenna coil electromagnetically coupled to a card reader. Having such a coupling coil electromagnetically coupled to the IC module, the IC cards described in JP H11-149536A and JP 2008-067057A can feed electrical power and transmit/receive signals with respect to the IC module without directly connecting the antenna coil and the IC module.

In order to extend communication distance between the IC card and the card reader, the number of turns of the antenna coil may be increased.

However, in an IC card having a coupling coil in addition to the antenna coil, there exist both a resistance component of the antenna coil and a resistance component of the coupling coil, so that an increase in the number of turns of the antenna coil leads to a further increase in the resistance component. Thus, in the IC card having the antenna coil and coupling coil, it is not easy to extend communication distance while suppressing the resistance components of the antenna coil and coupling coil.

SUMMARY

It is therefore an object of the present invention to provide an antenna device including an antenna coil and a coupling coil and an IC card having such an antenna device, in which communication distance is extended while the resistance components of the antenna coil and coupling coil are suppressed.

An antenna device according to the present invention includes: a substrate; a conductor pattern formed on the surface of the substrate and including a spiral or loop-shaped antenna coil, a spiral or loop-shaped coupling coil being connected to the antenna coil and having a diameter smaller than that of the antenna coil, and a spiral-shaped booster coil at least partially overlapping the antenna coil through the substrate without being connected thereto; and a resonance capacitor connected to the booster coil, wherein the number of turns of the booster coil is larger than that of the antenna coil.

According to the present invention, there is provided the booster coil that is electromagnetically coupled to the antenna coil without being connected thereto, so that it is possible to extend communication distance without increasing the number of turns of the antenna coil. In addition, the number of turns of the booster coil is larger than that of the antenna coil, so that it is possible to ensure a sufficient communication distance.

In the present invention, the substrate may have a rectangular shape, the antenna coil may be formed on one surface of the substrate along the sides thereof, and the booster coil may be formed on the other surface of the substrate along the sides thereof. With this configuration, the antenna coil and booster coil can each have a sufficiently large inner diameter area.

In the present invention, the coupling coil may be provided at a position overlapping the inner diameter areas of the respective antenna coil and booster coil and disposed offset to one short side of the substrate. With this configuration, an IC module can be disposed at a position overlapping the inner diameter areas of the respective antenna coil and booster coil and offset to the one short side of the substrate.

In the present invention, the resonance capacitor may be constituted by the conductor pattern and disposed offset to the other short side of the substrate. This can prevent mutual interference between the coupling coil and the resonance capacitor.

In the present invention, the conductor pattern may further include a matching capacitor connected in series or parallel to the antenna coil, and the matching capacitor may be provided at a position overlapping the inner diameter areas of the respective antenna coil and booster coil and disposed offset to the one short side of the substrate. With this configuration, the matching capacitor can be disposed in the vicinity of the coupling coil.

An IC card according to the present invention includes the above-described antenna device, a metal plate provided overlapping the antenna device, a magnetic sheet disposed between the antenna device and the metal plate, and an IC module electromagnetically coupled to a coupling coil.

According to the present invention, the IC card can perform communication with the card reader without being blocked by the metal plate.

In the present invention, the metal plate may have a first opening, the IC module may be disposed within the first opening, the magnetic sheet may have a second opening at a portion overlapping the IC module, and the coupling coil and IC module may be electromagnetically coupled to each other through the second opening. With this configuration, the coupling coil and IC module can be electromagnetically coupled to each other without being blocked by the magnetic sheet.

In the present invention, the inner diameter area of the coupling coil may completely overlap the second opening in a plan view, and the coil area of the coupling coil may completely overlap the second opening in a plan view. With this configuration, it is possible to sufficiently enhance the coupling strength between the coupling coil and the IC module.

In the present invention, the coupling coil may be formed on a surface of the substrate that is opposite to the surface facing the magnetic sheet. With this configuration, the coupling coil is not damaged in a process of forming the second opening in the magnetic sheet.

As described above, according to the present invention, in an antenna device including an antenna coil and a coupling coil and in an IC card having the antenna device, it is possible to extend communication distance while suppressing the resistance components of the antenna coil and coupling coil.

