Non-contact IC card and non-contact IC card reader/writer

• US 5,619,529 A
• Filed: 07/11/1995
• Issued: 04/08/1997
• Est. Priority Date: 07/20/1992
• Status: Expired due to Term

• Current Assignee: Renesas Electronics Corporation
• Original Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Inventors: Fujioka, Shuzo
• Primary Examiner(s): Chin, Stephen
• Assistant Examiner(s): WEBSTER, BRYAN E
• Application Number:
  US08/500,640
• Time in Patent Office: 637 Days
• Field of Search: 375/219, 375/220, 375/222, 375/238, 375/297, 375/345, 455/73, 455/127, 455/69, 235/492, 235/493, 235/380, 235/437, 364/480, 340/825.31, 340/825.33, 340/825.34, 340/825.3, 340/386, 340/318, 340/319, 379/144, 370/8, 370/9
• US Class Current: 375/219
• 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

A non-contact IC card or a non-contact IC card reader/writer has an antenna for receiving a signal transmitted from the reader/writer or the IC card, a receiver circuit for demodulating the signal received by the receiving antenna and for converting the demodulated signal into a received data signal, a control circuit for data processing in response to the received data signal, a transmitter circuit for forming a transmission signal in response to a data signal supplied by the control circuit and for setting the transmission width of the transmission signal corresponding to one data bit to a value smaller than the signal width of one data bit, and a transmitting antenna for transmitting the transmission signal from the transmitter circuit to the reader/writer or the IC card. According to a data transmission method of the invention, a data row having a first data item as dummy data is transmitted from the non-contact IC card to the reader/writer and the amplification of the received signal in the reader/writer is controlled so that the intensity of the received dummy data is equal to a predetermined value.

Claims

1. A non-contact IC card comprising:

receiving antenna means for receiving a signal transmitted from a reader/writer;

a receiver circuit for demodulating the signal received by said receiving antenna means and for converting the demodulated signal into a received data signal having signal units with respective durations corresponding to a duration of one data bit, said receiver circuit comprising;

a first amplifier circuit having a gain for amplifying the signal received by said receiving antenna means;

a detector circuit for demodulating the received signal amplified by said first amplifier circuit;

an automatic gain control circuit for controlling the gain of said first amplifier circuit upon reception of a signal received from an IC card, the signal received including a data row initially including dummy data, so that the intensity of the dummy data received from the IC card is equal to a predetermined intensity, whereby the received signal demodulated by said detector circuit has a constant intensity; and

a bit width generation circuit for converting the received signal demodulated by said detector circuit into the received data signal having the signal units with respective durations corresponding to the duration of one data bit;

a control circuit for data processing in response to the received data signal converted by said receiver circuit;

a transmitter circuit for forming a transmission signal in response to a data signal supplied by said control circuit, said transmitting circuit comprising;

a modulator circuit for forming the transmission signal in response to the data signal supplied by said control circuit; and

a second amplifier circuit for amplifying the transmission signal from said modulator circuit and for outputting the amplified transmission signal to said transmitting antenna means, said automatic gain control circuit controlling the gain of said second amplifier circuit of said transmitter circuit; and

transmitting antenna means for transmitting the transmission signal from said transmitter circuit to the reader/writer.

2. A non-contact IC card reader/writer comprising:

receiving antenna means for receiving a signal transmitted from an IC card;

a receiver circuit for demodulating the signal received by said receiving antenna means and for converting the demodulated received signal into a received data signal having signal units with respective durations corresponding to a duration of one data bit, said receiver circuit comprising;

a first amplifier circuit having a gain for amplifying the signal received by said receiving antenna means;

a detector circuit for demodulating the received signal amplified by said first amplifier circuit;

an automatic gain control circuit for controlling the gain of said first amplifier circuit upon reception of a signal received from an IC card, the signal received including a data row initially including dummy data, so that the intensity of the dummy received from the IC card is equal to a predetermined intensity, whereby the received signal demodulated by said detector circuit has a constant intensity; and

a bit width generation circuit for converting the received signal demodulated by said detector circuit into the received data signal having the signal units with respective durations corresponding to the duration of one data bit;

a control circuit for data processing in response to the received data signal converted by said receiver circuit;

a transmitter circuit for forming a transmission signal in response to a data signal supplied by said control circuit; and

transmitting antenna means for transmitting the transmission signal from said transmitter circuit to the IC card.

3. The reader/writer according to claim 2 wherein said transmitter circuit includes:

a modulator circuit for forming a transmission signal in response to the data signal supplied by said control circuit; and

a second amplifier circuit for amplifying the transmission signal from said modulator circuit and for outputting the amplified transmission signal to said transmitting antenna means, said automatic gain control circuit controlling the gain of said second amplifier circuit of said transmitter circuit.