Modulation, demodulation and antenna coupling circuits used in IC card reading/writing apparatus, and method of supplying power to the IC card

• US 5,898,738 A
• Filed: 05/23/1997
• Issued: 04/27/1999
• Est. Priority Date: 12/22/1994
• Status: Expired due to Term

• Current Assignee: Renesas Electronics Corporation
• Original Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Inventors: Takahira, Kenichi, Nagata, Yoshishige
• Primary Examiner(s): Pham, Chi H.
• Assistant Examiner(s): WEBSTER, BRYAN E
• Application Number:
  US08/863,044
• Time in Patent Office: 704 Days
• Field of Search: 375/308, 375/362, 375/364, 375/354, 375/371, 375/326, 375/340, 375/327, 375/329, 329/306-309, 235/492, 235/493
• US Class Current: 375/326
• 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: H04L 27/18 Phase-modulated carrier systems, i.e. using phase-shift keying H04L27/32 takes precedence
• CPC Class Codes: H04L 27/2332 using a non-coherent carrier

Abstract

A modulator used in an IC card reader/writer includes a phase variation detector for detecting a varying point of the phase of a modulated signal, a signal processing circuit for modifying the modulated signal for a half period at the phase varying point to have a frequency and amplitude twice those of the modulated signal, a first Miller integrator for integrating the modified signal to produce a triangular wave signal, and a second Miller integrator for integrating the triangular wave signal to produce a sinusoidal wave signal having a continuous phase. A demodulator used in the reader/writer includes a sync control circuit which controls a carrier sync signal generation circuit thereby to control the phase of a carrier sync signal in response to the discrimination as to whether the carrier sync signal is in lead-phase or lag-phase relative to the signal modulated based on binary phase shift keying (BPSK). A control data signal and non-modulated carrier wave sent from the reader/writer to the IC card are converted into power for use by the IC card.

Claims

1. A modulation circuit used in an IC card reading/writing apparatus comprising:

a differential encoder for performing differential encoding for a signal to be sent to an IC card;

a modulator for implementing the binary phase shift keying modulation based on the exclusive logical sum operation for the encoded signal and a pulse signal having a carrier frequency;

a phase change detector for detecting a change point of the phase of the modulated signal;

a signal processing circuit for modifying the modulated signal for a half cycle at the phase change point to have a frequency and an amplitude twice those of the modulated signal;

a first Miller integration circuit which integrates the modified signal to produce a triangular wave signal; and

a second Miller integration circuit which integrates the triangular wave signal provided by said first Miller integration circuit to produce a sinusoidal wave signal having a continuous phase.

2. A modulation circuit according to claim 1, wherein said signal processing circuit includes:

an additive pulse generator for generating a 1-cycle pulse signal having a frequency twice the carrier frequency at the time of phase varying point;

an inverting circuit for inverting the modulated signal;

a first logical sum circuit which receives the modulated signal and the pulse signal provided by the additive pulse generator;

a second logical sum circuit which receives the inverted modulated signal provided by said inverting circuit and the pulse signal provided by the additive pulse generator; and

voltage summing means for summing the output voltages of said first and second logical sum circuits.

3. A modulation circuit according to claim 2, wherein said voltage summing means includes:

a first resistor having one end connected to the output of said first logical sum circuit and another end connected to the inverting input terminal of an operational amplifier in said first Miller integration circuit; and

a second resistor having one end connected to the output of said second logical sum circuit and another end connected to the inverting input terminal of said operational amplifier,

said first and second resistors having resistance values set to be 1;

3 ratio and functioning as summing resistors of said operational amplifier and also as input resistors of said first Miller integration circuit.

4. An antenna coupling circuit used in an IC card reading/writing apparatus for delivering a signal received by an antenna of said apparatus to a receiver of said apparatus and feeding a signal from a transmitter of said apparatus to said antenna, said antenna coupling circuit comprising:

a coupling transformer having an antenna coil connected to said antenna, a receiving coil, and a sending coil connected to said transmitter;

an operational amplifier having one input terminal connected to said receiving coil of said coupling transformer and an output terminal connected to said receiver; and

resistors which divide an output voltage of said transmitter and delivers the divided voltage to another input of said operational amplifier,

said divided voltage having such an amplitude as to offset on said operational amplifier a transmitter output voltage induced on said receiving coil of said coupling transformer.

5. An antenna coupling circuit used in an IC card reading/writing apparatus for delivering a signal received by an antenna of said apparatus to a receiver of said apparatus and feeding a signal from a transmitter of said apparatus to said antenna, said antenna coupling circuit comprising:

a coupling transformer having an antenna coil connected to said antenna, and a transmitting/receiving coil connected to said transmitter;

an operational amplifier having one input terminal connected to said receiving coil of said coupling transformer and an output terminal connected to said receiver; and

resistors which divide an output voltage of said transmitter and delivers the divided voltage to another input of said operational amplifier,

said divided voltage having such an amplitude as to offset on said operational amplifier a transmitter output voltage induced on said transmitting/receiving coil of said coupling transformer.

6. A method of supplying power from an IC card reading/writing apparatus to an IC card, said method comprising the steps of:

transmitting a control data signal from said reading/writing apparatus;

transmitting a non-modulated carrier wave for power supply from said reading/writing apparatus to said IC card subsequently to the transmitting of said control data signal;

receiving the control data signal and the non-modulated carrier wave on the part of said IC card, and converting continuously the control data signal and the carrier wave into power to be used by said IC card; and

transmitting a data signal from said IC card to said reading/writing apparatus during a period of receiving the carrier wave following the reception of the control data signal transmitted from said reading/writing apparatus.

7. A method of supplying power from an IC card reading/writing apparatus to an IC card comprising:

a first step of transmitting a control data signal from said reading/writing apparatus to said IC card;

a second step, on the part of said IC card, of receiving the control data signal and converting the signal into power to be used by said IC card;

a third step of transmitting a data signal from said IC card to said reading/writing apparatus;

a fourth step of transmitting a non-modulated carrier wave for power supply from said reading/writing apparatus to said IC card;

a fifth step of receiving the non-modulated carrier wave and converting the carrier wave into power to be used by said IC card; and

a sixth step of transmitting a data signal from said IC card to said reading/writing apparatus; and

a seventh step of repeating said fourth through sixth steps.

8. An IC card reading/writing apparatus for reading and writing data to and from an IC card, comprising:

a modulation circuit, including

a differential encoder for performing differential encoding for a signal to be sent to an IC card,

a modulator for implementing a binary phase shift keying modulation based on an exclusive logical sum operation for the encoded signal and a pulse signal having a carrier frequency,

a phase change detector for detecting a change point of the phase of the modulated signal,

a signal processing circuit for modifying the modulated signal for a half cycle at the phase change point to have a frequency and an amplitude twice those of the modulated signal,

a first Miller integration circuit which integrates the modified signal to produce a triangular wave signal, and

a second Miller integration circuit which integrates the triangular wave signal provided by said first Miller integration circuit to produce a sinusoidal wave signal having a continuous phase;

an antenna coupling circuit for delivering a signal received by an antenna of said apparatus to a receiver of said apparatus and feeding a signal from a transmitter of said apparatus to said antenna, including

a coupling transformer having an antenna coil connected to said antenna, a receiving coil, and a sending coil connected to said transmitter,

an operational amplifier having one input terminal connected to said receiving coil of said coupling transformer and an output terminal connected to said receiver, and

resistors which divide an output voltage of said transmitter and deliver the divided voltage to another input of said operational amplifier,

said divided voltage having an amplitude such as to offset on said operational amplifier a transmitter output voltage induced on said receiving coil of said coupling transformer; and

means for supplying power from the IC card reading/writing apparatus to the IC card, including

means for transmitting a control data signal from said reading/writing apparatus,

means for transmitting a non-modulated carrier wave for power supply from said reading/writing apparatus to said IC card subsequent to the transmitting of said control data signal,

means on said IC card for receiving the control data signal and the non-modulated carrier wave, and for continuously converting the control data signal and the carrier wave into power to be used by said IC card, and

means for transmitting a data signal from said IC card to said reading/writing apparatus during a period of receiving the carrier wave following the reception of the control data signal transmitted from said reading/writing apparatus.