Contactless IC card system

• US 6,198,361 B1
• Filed: 06/07/1999
• Issued: 03/06/2001
• Est. Priority Date: 06/10/1998
• Status: Expired due to Term

• Current Assignee: Sony Corporation (Sony Group Corp.)
• Original Assignee: Sony Corporation (Sony Group Corp.)
• Inventors: Arisawa, Shigeru
• Primary Examiner(s): MIS, DAVID C
• Application Number:
  US09/327,757
• Time in Patent Office: 638 Days
• Field of Search: 332/115, 332/116, 327/178, 327/179, 327/180, 375/353
• US Class Current: 332/115
• CPC Class Codes: G06K 19/0723 the record carrier comprising an arrangement for non-contact communication, e.g. wireless communication circuits on transponder cards, non-contact smart cards or RFIDs
• CPC Class Codes: G06K 7/0008 General problems related to the reading of electronic memory record carriers, independent of its reading method, e.g. power transfer
• CPC Class Codes: H03C 1/08 by means of variable impedance element H03C1/28 - H03C1/34, H03C1/46 - H03C1/52, H03C1/62 take precedence
• CPC Class Codes: H03C 1/14 the element being a diode
• CPC Class Codes: H03C 1/36 by means of semiconductor device having at least three electrodes H03C1/34, H03C1/50, H03C1/52, H03C1/62 take precedence
• CPC Class Codes: H03F 2200/327 Amplitude shift keying modulation being used in an amplifying circuit
• CPC Class Codes: H03F 2203/7215 the gated amplifier being switched on or off by a switch at the input of the amplifier
• CPC Class Codes: H03F 3/72 Gated amplifiers, i.e. amplifiers which are rendered operative or inoperative by means of a control signal
• CPC Class Codes: H03K 7/02 Amplitude modulation, i.e. PAM
• CPC Class Codes: H04L 27/04 Modulator circuits; Transmitter circuits
• CPC Class Codes: H04L 27/06 Demodulator circuits; Receiver circuits

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.

Claims

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 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.

2. A modulating circuit as claimed in claim 1, wherein

said first output signal has a same phase as that of said input signal; and

means outputs said second output signal has a phase opposite to that of said input signal.

3. A modulating circuit as claimed in claim 1, wherein

said first signal output means power-amplifies said first output signal to output a power-amplified first output signal;

and

said second signal output means power-amplifies said second output signal to output a power-amplified second output signal.

4. A modulating circuit as claimed in claim 1, wherein

said input signal is a sine wave signal having a single frequency.

5. A modulating circuit as claimed in claim 1, wherein

said input signal is a rectangular wave signal having a single frequency.

6. A modulating circuit as claimed in claim 5, wherein

said second signal output means outputs said second output signal having a phase opposite to that of said input signal by inverting the logic level of said input signal.

7. A modulating circuit as claimed in claim 3, wherein

said gate means controls a stopping of the power amplifying operation by said second signal output means so as to gate said second output signal;

and

said second signal output means maintains an impedance of an output terminal at a high impedance for a time period during which the power amplifying process operation is stopped.

8. A modulating circuit as claimed in claim 3, wherein

at least one of said first output signal means and said second output signal means provide its respective power-amplified output signal to a switching circuit for switching operations in response to said input signal.

9. A modulating circuit as claimed in claim 3, wherein

at least said second signal output means and said gate means are tri-state buffer circuits.