Contactless IC card system

• US 7,609,109 B2
• Filed: 03/19/2007
• Issued: 10/27/2009
• Est. Priority Date: 06/10/1998
• Status: Expired due to Fees

• 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:
  US11/688,121
• Publication Number:
  US 20070170985A1
• Time in Patent Office: 953 Days
• Field of Search: 329/311, 329/370, 375/353
• 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: signal processing means for producing first and second input signals; 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 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.

Claims

1. A demodulating circuit, comprising:

signal processing means for producing first and second input signals, wherein a phase of the first input signal is approximately 180 degrees different from a phase of the second input signal;

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 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.

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

said first and second clamping means are configured as a grounded type diode.

3. 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.

4. A demodulating circuit as claimed in claim 1, wherein the first and second input signals are amplitude-modulated signals.