Contactless IC card system
First Claim
1. A modulating circuit comprising:
- first signal output means for outputting a first output signal having a first predetermined phase with respect to that of an input signal;
second signal output means for outputting a second output signal having a second predetermined phase with respect to that of said input signal;
gate means for gating at least second output signal;
calculation means for adding or subtracting said first output signal and said second output signal; and
controls means for controlling the operation of said gate means in response to a logic level of input data, wherein said first signal output means outputs said first output signal from a first antenna;
said second signal output means outputs said second output signal from a second antenna; and
said calculation means is formed by way of an electromagnetic coupling between said first antenna and said second antenna.
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Accused Products
Abstract
In a contactless IC card system, a modulating circuit manufactured in an IC form is operable at a high power efficiency. The demodulating apparatus is configured to include: first signal output means for outputting a first output signal having a predetermined phase with respect to that of an input signal, a second signal output means for outputting a second output signal having a predetermined phase with respect to that of the input signal, gate means for gating at least the second output signal, calculation means for adding, or subtracting the first output signal and the second output signal; and control means for controlling the operation of the gate means in response to a logic level of input data.
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Citations
22 Claims
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1. A modulating circuit comprising:
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first signal output means for outputting a first output signal having a first predetermined phase with respect to that of an input signal;
second signal output means for outputting a second output signal having a second predetermined phase with respect to that of said input signal;
gate means for gating at least second output signal;
calculation means for adding or subtracting said first output signal and said second output signal; and
controls means for controlling the operation of said gate means in response to a logic level of input data, wherein said first signal output means outputs said first output signal from a first antenna;
said second signal output means outputs said second output signal from a second antenna; and
said calculation means is formed by way of an electromagnetic coupling between said first antenna and said second antenna.
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2. An amplifying circuit in which an operation of a field-effect transistor is switched in response to an input signal so as to output a power-amplified signal of said input signal from said field-effect transistor, comprising:
a drive circuit for switching the operation of said field-effect transistor by applying a voltage to a gate of said field-effect transistor, said voltage being higher than or equal to a source-to-drain voltage of said field-effect transistor. - View Dependent Claims (3)
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4. An amplifying circuit, comprising:
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first variable resistor means, one end of which is held at a first potential and the resistance value of which is varied in response to a first control signal;
second variable resistor means, one end of which is connected to the other end of said first variable resistor means, the other end of which is held at a second potential different from said first potential and the resistance value of which is varied in response to a second control signal; and
control means for switching a signal level of said first control signal and a signal level of said second control signal so as to switch a potential at a connection center point between said first variable resistor means and said second variable resistor means to another potential corresponding to said first and second potentials, and also so as to switch an impedance of said connection center point to a high impedance in response to both an input signal and a control signal. - View Dependent Claims (5, 6)
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7. A transmitter apparatus for amplitude-modulating input data by using a modulating circuit to thereby transmit the amplitude-modulated input data, wherein
said modulating circuit comprises: -
first signal output means for outputting a first output signal having a predetermined phase with respect to that of an input signal;
a second signal output means for outputting a second output signal having a predetermined phase with respect to that of said input signal;
gate means for gating at least said second output signal;
calculation means for adding or subtracting said first output signal and said second output signal; and
control means for controlling the operation of said gate means in response to a logic level of input data. - View Dependent Claims (8)
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9. A transmitter apparatus for amplitude-modulating input data to thereby transmit the amplitude-modulated input data, comprising:
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a first modulating circuit for producing a first amplitude-modulated signal in response to said input data; and
a second modulating circuit for producing a second amplitude-modulated signal made of a carrier wave having a phase opposite to that of said first amplitude-modulated signal, wherein each of said first modulating circuit and said second modulating circuit comprises;
first signal output means for outputting a first output signal having a first predetermined phase with respect to that of an input signal;
a second signal output means for outputting a second output signal having a second predetermined phase with respect to that of said input signal;
gate means for gating at least said second output signal;
calculation means for adding, or subtracting said first output signal and said second output signal; and
control means for controlling the operation of said gate means in response to a logic level of input data.
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10. A modulating circuit, comprising:
a variable attenuator provided at an output terminal of a power amplifying circuit, for attenuating a power-amplified result of said power amplifying circuit in response to an input signal. - View Dependent Claims (11, 12)
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13. A transmitter apparatus for amplitude-modulating an input signal to thereby transmit the amplitude-modulated input signal, comprising:
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a first modulating circuit for producing a first amplitude-modulated signal in response to said input signal; and
a second modulating circuit for producing a second amplitude-modulated signal made of a carrier wave having a phase opposite to that of said first amplitude-modulated signal in response to said input signal, wherein each of said first modulating circuit and said second modulating circuit comprises;
a variable attenuator provided at an output terminal of a power amplifying circuit, for attenuating a power-amplified result of said power amplifying circuit in response to an input signal.
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14. A demodulating circuit comprising:
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clamping means for clamping an input signal; and
band limiting means for removing a component of said input signal from an output signal of said clamping means. - View Dependent Claims (15, 16)
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17. A demodulating circuit, comprising:
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signal processing means for producing first and second input signals having phases different from a phase of an input signal by approximately 180 degrees;
first clamping circuit for clamping said first input signal;
second clamping circuit for clamping said second input signal;
first band limiting means for removing a component of said first input signal from an output signal of said first clamping circuit;
second band limiting means for removing a component of said second input signal from an output signal of said first clamping means; and
calculating means for adding, or averaging an output signal of said first band limiting means and an output signal of said second band limiting means. - View Dependent Claims (18, 19)
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20. A demodulating circuit, comprising:
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signal processing means for producing first and second input signals having phases different from a phase of an input signal by approximately 180 degrees;
a first clamping circuit for clamping said first input signal;
a second clamping circuit for clamping said second input signal;
first band limiting means for removing a component of said first input signal from an output signal of said first clamping circuit; and
second band limiting means for removing a component of said second input signal from an output signal of said second clamping circuit; and
calculating means for adding, or averaging an output signal of said first band limiting means and an output signal of said second band limiting means. - View Dependent Claims (21, 22)
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Specification