Transmitter-receiver for non-contact IC card system

• US 5,703,573 A
• Filed: 01/11/1996
• Issued: 12/30/1997
• Est. Priority Date: 01/11/1995
• Status: Expired due to Term

• Current Assignee: Sony Chemicals Corp. (Dexerials Corporation)
• Original Assignee: Sony Chemicals Corp. (Dexerials Corporation)
• Inventors: Fujimoto, Masahiro, Orihara, Katsuhisa
• Primary Examiner(s): Horabik, Michael
• Assistant Examiner(s): MERZ, EDWARD W
• Application Number:
  US08/584,284
• Time in Patent Office: 719 Days
• Field of Search: 340/825.54, 340/825.34, 340/825.72, 340/825.36, 340/825.49, 342/42, 342/44, 342/47
• US Class Current: 340/10.3
• CPC Class Codes: G01S 13/75 using transponders powered from received waves, e.g. using passive transponders , or using passive reflectors
• CPC Class Codes: G01S 13/82 wherein continuous-type signals are transmitted
• CPC Class Codes: G06K 19/0707 the arrangement being capable of collecting energy from external energy sources, e.g. thermocouples, vibration, electromagnetic radiation G06K19/0702 takes precedence
• CPC Class Codes: G06K 19/0712 the arrangement being capable of triggering distinct operating modes or functions dependent on the strength of an energy or interrogation field in the proximity of the record carrier active means for hindering electromagnetic reading or writing G06K19/07336
• CPC Class Codes: G06K 19/0715 the arrangement including means to regulate power transfer to the integrated circuit
• 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

Abstract

In a non-contact IC card system which transmits and receives signals between an interrogator and a transponder, a transmitter-receiver used for the interrogator comprises a distance detecting means for detecting the distance between the interrogator and the transponder, and an output control means for controlling the output level of the interrogator in accordance with the signals detected by the distance detecting means, so as to keep the receiving level of the transponder within the range of a given value. The receiving level in the transponder can be prevented from varying depending on the distance between the interrogator and the transponder, so that it becomes unnecessary to provide a protective circuit against an excessive increase of the receiving level. The optimum threshold voltage can also be prevented from varying.

Claims

1. A transmitter-receiver used for an interrogator in a non-contact IC card system which transmits and receives signals between the interrogator and a transponder;

said transmitter-receiver comprising;

a distance detecting means for detecting the distance between the interrogator and the transponder; and

an output control means for controlling the output level of the interrogator in accordance with the signals detected by the distance detecting means, so as to keep the receiving level of the transponder within the range of a given value.

2. The transmitter-receiver for a non-contact IC card system according to claim 1, wherein said distance detecting means detects an antenna coupling coefficient between the interrogator and the transponder, and the output control means controls the output level in accordance with a reciprocal of the antenna coupling coefficient detected by said distance detecting means.