Antenna device of interrogator
First Claim
1. An antenna device of an interrogator having a resonance frequency of a predetermined value which constitutes an automatic identification system by exchanging information with an IC tag attached to an object to be identified by electromagnetic coupling, comprising:
- an antenna element including an antenna coil fabricated from at least one turn of an electrically conductive material, a resistance component and an inductance component connected in series with the antenna coil; and
a capacitor which is connected in series to said antenna element with the resistance component disposed between the capacitor and the inductance component, the capacitor having a variable capacitance to maintain the resonance frequency of the antenna device at the predetermined value.
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Accused Products
Abstract
An antenna device of an interrogator which constitutes an automatic identification system by exchanging information with an IC tag attached to an object to be identified by electromagnetic coupling is disclosed. The antenna device comprises an antenna element, and a capacitor connected in series to the antenna element and having a variable capacitance to maintain a predetermined resonance frequency. The predetermined resonance frequency is maintained by switching taps on an antenna coil. Alternatively, the predetermined resonance frequency is maintained by switching taps on a tapped inductor or by a variable inductor.
180 Citations
14 Claims
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1. An antenna device of an interrogator having a resonance frequency of a predetermined value which constitutes an automatic identification system by exchanging information with an IC tag attached to an object to be identified by electromagnetic coupling, comprising:
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an antenna element including an antenna coil fabricated from at least one turn of an electrically conductive material, a resistance component and an inductance component connected in series with the antenna coil; and a capacitor which is connected in series to said antenna element with the resistance component disposed between the capacitor and the inductance component, the capacitor having a variable capacitance to maintain the resonance frequency of the antenna device at the predetermined value. - View Dependent Claims (2, 6, 9, 12)
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3. An antenna device of an interrogator having a resonance frequency of a predetermined value which constitutes an automatic identification system by exchanging information with an IC tag attached to an object to be identified by electromagnetic coupling, comprising:
an antenna element including an antenna coil fabricated from at least one turn of an electrically conductive material, a resistance component, a tapped inductor and a fixed capacitor connected in series with the antenna coil with the resistance component disposed between the tapped inductor and the fixed capacitor, the tapped inductor having taps which are switched from one to another to maintain the resonance frequency of the antenna device at the predetermined value. - View Dependent Claims (5, 10, 11)
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4. An antenna device of an interrogator having a resonance frequency of a predetermined value which constitutes an automatic identification system by exchanging information with an IC tag attached to an object to be identified by electromagnetic coupling, comprising:
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an antenna element including an antenna coil fabricated from at least one turn of an electrically conductive material, a resistance component, an inductance component and a fixed capacitor connected in series with the antenna coil with the resistance component disposed between the inductance component and the fixed capacitor; and a tapped inductor which is connected in series to said antenna element and having taps which are switched from one to another to maintain the resonance frequency of the antenna device at the predetermined value. - View Dependent Claims (13)
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7. An antenna device of an interrogator having a resonance frequency of a predetermined value which constitutes an automatic identification system by exchanging information with an IC tag attached to an object to be identified by electromagnetic coupling, comprising:
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an antenna element including an antenna coil fabricated from at least one turn of an electrically conductive material, a resistance component and a fixed capacitor connected in series with the antenna coil; and a variable inductor, connected in series to said antenna coil with the resistance component disposed between the variable inductor and the fixed capacitor, the variable inductor operative for maintaining the resonance frequency of the antenna device at the predetermined value. - View Dependent Claims (8, 14)
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Specification