Contactless IC card system

• US 6,784,730 B2
• Filed: 05/21/2003
• Issued: 08/31/2004
• 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:
  US10/442,736
• Publication Number:
  US 20030199255A1
• Time in Patent Office: 468 Days
• Field of Search: 329/300, 329/304, 329/311-315, 329/347, 375/320, 375/340
• US Class Current: 329/311
• 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 demodulating circuit, comprising:

polarity judging means for judging a polarity of an amplitude-modulated signal to thereby output a polarity judgment result;

multiplying means for multiplying said polarity judgment result by said amplitude-modulated signal to thereby output a multiplication result; and

band, limiting means for removing a component of said amplitude-modulated signal from said multiplication result.

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

said polarity judging means is configured as a limiter for limiting an amplitude of said amplitude-modulated signal on a positive side and on a negative side.

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

said multiplying means is configured as a double balanced mixer.

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

said band limiting means comprises to any one of a low-pass filter, a band-pass filter and a trap filter.

5. A demodulating circuit, comprising:

signal producing means for producing from an amplitude-modulated signal first and second amplitude-modulated signals having phases inverted from each other;

polarity judging means for judging a polarity of one of said amplitude-modulated signal, said first amplitude-modulated signal, and said second amplitude-modulated signal to thereby output a polarity judgment result;

selecting/outputting means for selectively outputting said first amplitude-modulated signal and said second amplitude-modulated signal based upon said polarity judgment result; and

band limiting means for removing a component of said amplitude-modulated signal from the output signal of said selecting/outputting means.

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

said band limiting means comprises to any one of a low-pass filter, a band-pass filter, and a trap filter.