ANTENNA DEVICE AND COMMUNICATION DEVICE
First Claim
1. An antenna device comprising:
- a resonance circuit including an antenna coil, receiving a magnetic field transmitted at preset an oscillation frequency from a transmitter, and a capacitor electrically connected to the antenna coil;
the resonance circuit being inductively coupled to the transmitter to provide for a transmission enabled state; and
a magnetic sheet provided at a face-to-face position with respect to the antenna coil and configured for changing the inductance of the antenna coil;
the capacitor having a temperature characteristic in which the capacitance of the capacitor is changed with changes in temperature within a working temperature range;
the magnetic sheet being formed of a magnetic material having a temperature characteristic in which the inductance of the antenna coil is changed with a characteristic opposite to that of the capacitance of the capacitor, changed with changes in temperature in the working temperature range, so that the resonance frequency of the resonance circuit in the working temperature range will be brought into coincidence approximately with the oscillation frequency.
2 Assignments
0 Petitions
Accused Products
Abstract
An antenna device includes an antenna coil that receives a magnetic field transmitted from a reader/writer and a capacitor. The antenna device also includes a magnetic sheet formed at a face-to-face position with respect to the antenna coil and configured for changing the inductance of the antenna coil. The capacitor has a temperature characteristic in which the capacitance of the capacitor is changed with changes in temperature. The magnetic sheet is formed of a magnetic material having a temperature characteristic in which the inductance of the antenna coil is made to be changed with an opposite sign of change to that of the capacitance of the capacitor that is changed with changes in temperature in the working temperature range. In this manner, the resonance frequency of the antenna circuit in the working temperature range may be brought approximately into coincidence with the oscillation frequency of the reader/writer.
26 Citations
9 Claims
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1. An antenna device comprising:
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a resonance circuit including an antenna coil, receiving a magnetic field transmitted at preset an oscillation frequency from a transmitter, and a capacitor electrically connected to the antenna coil;
the resonance circuit being inductively coupled to the transmitter to provide for a transmission enabled state; anda magnetic sheet provided at a face-to-face position with respect to the antenna coil and configured for changing the inductance of the antenna coil; the capacitor having a temperature characteristic in which the capacitance of the capacitor is changed with changes in temperature within a working temperature range; the magnetic sheet being formed of a magnetic material having a temperature characteristic in which the inductance of the antenna coil is changed with a characteristic opposite to that of the capacitance of the capacitor, changed with changes in temperature in the working temperature range, so that the resonance frequency of the resonance circuit in the working temperature range will be brought into coincidence approximately with the oscillation frequency. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A communication device comprising:
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a resonance circuit including an antenna coil, receiving a magnetic field transmitted at preset an oscillation frequency from a transmitter, and a capacitor electrically connected to the antenna coil;
the resonance circuit being inductively coupled to the transmitter to provide for a transmission enabled state;a magnetic sheet provided at a face-to-face position with respect to the antenna coil and configured for changing the inductance of the antenna coil; and a communication processor driven by a current flowing through the resonance circuit to have communication with the transmitter; the capacitor having a temperature characteristic in which the capacitance of the capacitor is changed with changes in temperature in the working temperature range; the magnetic sheet being formed of a magnetic material having a temperature characteristic in which the inductance of the antenna coil is changed with a characteristic opposite to that of the capacitance of the capacitor so that the resonance frequency of the resonance circuit in the working temperature range will be brought into coincidence approximately with the oscillation frequency.
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Specification