RFID module
First Claim
Patent Images
1. An RFID module comprising:
- an antenna element forming an RFID antenna;
an RFID circuit block to which the antenna element is connected; and
a first resonance frequency adjustment circuit having an element that includes a drain terminal connected to the antenna element, a gate terminal that is grounded, a source terminal that is grounded, wherein a pull-up resistor is connected between the drain terminal and a power supply such that the drain terminal has separate connections to the antenna element and to the power supply,wherein a DC level of the drain terminal is configured to be decreased through a capacitance between the drain terminal and the gate terminal when an AC waveform of a predetermined amplitude or more is input on the basis of a voltage excited in the RFID antenna when the RFID module comes close to an R/W device, andthe first resonance frequency adjustment circuit is configured to shift a resonance frequency of a loop antenna toward lower frequencies by increasing a drain-source parasitic capacitance value on the basis of the decrease of the DC level of the drain terminal.
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Abstract
An RFID module including an antenna element forming an RFID antenna; an RFID circuit block to which the antenna element is connected; and a first resonance frequency adjustment circuit having an element that includes a drain terminal connected to the antenna element, a gate terminal that is grounded, and a source terminal that is grounded, wherein a pull-up resistor is connected between the drain terminal and a power supply.
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Citations
13 Claims
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1. An RFID module comprising:
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an antenna element forming an RFID antenna; an RFID circuit block to which the antenna element is connected; and a first resonance frequency adjustment circuit having an element that includes a drain terminal connected to the antenna element, a gate terminal that is grounded, a source terminal that is grounded, wherein a pull-up resistor is connected between the drain terminal and a power supply such that the drain terminal has separate connections to the antenna element and to the power supply, wherein a DC level of the drain terminal is configured to be decreased through a capacitance between the drain terminal and the gate terminal when an AC waveform of a predetermined amplitude or more is input on the basis of a voltage excited in the RFID antenna when the RFID module comes close to an R/W device, and the first resonance frequency adjustment circuit is configured to shift a resonance frequency of a loop antenna toward lower frequencies by increasing a drain-source parasitic capacitance value on the basis of the decrease of the DC level of the drain terminal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A portable device comprising:
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a display unit that provides a display interface to a user; an operation unit that provides an input interface to the user; an RFID unit; and a control unit that performs control of each unit and data processing, wherein the RFID unit includes; an antenna element forming an RFID antenna; an RFID circuit block to which the antenna element is connected; and a resonance frequency adjustment circuit having an element that includes a drain terminal connected to the antenna element, a gate terminal that is grounded, and a source terminal that is grounded, wherein a pull-up resistor is connected between the drain terminal and a power supply, such that the drain terminal has separate connections to the antenna element and to the power supply, wherein a DC level of the drain terminal is configured to be decreased through a capacitance between the drain terminal and the gate terminal when an AC waveform of a predetermined amplitude or more is input on the basis of a voltage excited in the RFID antenna when the RFID unit comes close to an R/W device, and the first resonance frequency adjustment circuit is configured to shift a resonance frequency of a loop antenna toward lower frequencies by increasing a drain-source parasitic capacitance value on the basis of the decrease of the DC level of the drain terminal.
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13. A communication method for an RFID module having an antenna element forming an RFID antenna, an RFID circuit block to which the antenna element is connected, and a resonance frequency adjustment circuit, the method comprising:
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connecting a source grounded element of the resonance frequency adjustment circuit to one end of the antenna element; pulling up a drain terminal of the source grounded element to a power-supply voltage through a pull-up resistor; grounding the gate terminal of the source grounded element; decreasing a DC level of the drain terminal of the source grounded element through a capacitance between the drain terminal and the gate terminal when an AC waveform of a predetermined amplitude or more is input on the basis of a voltage excited in the RFID antenna when the RFID module comes close to an R/W device; and shifting a resonance frequency of a loop antenna toward lower frequencies by increasing a drain-source parasitic capacitance value on the basis of the decrease of the DC level.
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Specification