RFID tag, RFID reader/writer, RFID system, and processing method of RFID system

• US 20070176772A1
• Filed: 07/25/2006
• Published: 08/02/2007
• Est. Priority Date: 10/19/2005
• Status: Active Grant

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Watanabe, Kazuki, Yazawa, Yoshiaki, Nemoto, Ryo, Yoshigi, Hiroshi
• Granted Patent: US 7,944,338 B2
• Time in Patent Office: Days
• US Class Current: 340/539.220
• CPC Class Codes: G06K 19/0701 at least one of the integrated circuit chips comprising an arrangement for power management
• CPC Class Codes: G06K 19/0717 the sensor being capable of sensing environmental conditions such as temperature history or pressure
• 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

Abstract

In an RFID system including RFID tags each incorporating a sensor, accuracy of measurement by the sensor can be improved. For example, when measurements are performed several times by using RFID tags each incorporating a sensor unit, generation of a carrier directed from an RFID reader/writer to the RFID tags is stopped for a predetermined period every time when a measurement ends. By this means, the chip temperature of the RFID tag increased due to power consumption in each measurement can be reduced to, for example, ambient temperature every time when a measurement ends. Therefore, an error in measurement by the sensor unit can be reduced, thereby achieving accurate measurement.

Claims

1. An RFID system comprising:

RFID tags each having a communication circuit, a control circuit, and a sensor circuit integrated on one semiconductor chip; and

an RFID reader/writer capable of wireless communication with said RFID tags,

wherein said system includes a function to cut off power supply to the internal circuits of said RFID tags for a predetermined period during each interval between measurements, when the measurements are successively performed several times by using said sensor circuit.

2. The RFID system according to claim 1,

wherein each of said measurements includes a first processing step of performing various processes before execution of measurement and a second processing step of performing the measurement by using said sensor circuit and then processing results of said measurement, and

said predetermined period in which power supply is cut off is a period between an end of said second processing step and a start of said first processing step.

3. The RFID system according to claim 1,

wherein each of said measurements includes a first processing step of performing various processes before execution of measurement and a second processing step of performing the measurement by using said sensor circuit and then processing results of said measurement, and

said predetermined period in which power supply is cut off is a period between an end of said first processing step and a start of said second processing step.

4. The RFID system according to claim 1,

wherein said function to cut off power supply is achieved by cutting off a carrier signal directed from said RFID reader/writer to said RFID tags.

5. The RFID system according to claim 1,

wherein said function to cut off power supply is achieved by providing each of said RFID tags with a power supply cutoff circuit capable of controlling cutoff/resumption of power supply to the internal circuits of said RFID tags.

6. The RFID system according to claim 1,

wherein each of said measurements includes a first processing step of performing various processes before execution of measurement and a second processing step of performing measurements several times by using said sensor circuit and then processing results of said measurements,

said predetermined period in which power supply is cut off is a period between an end of said first processing step and a start of said second processing step and a period between an end of said second processing step and a start of said first processing step, and

said RFID system includes a function to correct an error due to self heating of said RFID tag based on the measurement results obtained through the measurements performed several times in said second processing step and then calculate one measurement result for said second processing step.

7. An RFID tag comprising circuits integrated on one semiconductor chip, said circuits including:

a communication circuit having a modulation function and a demodulation function and performing wireless communication with an RFID reader/writer;

a sensor circuit capable of performing various measurements;

a control circuit which controls said communication circuit and said sensor circuit; and

a power supply circuit which supplies power to said communication circuit, said sensor circuit, and said control circuit,

wherein said power supply circuit includes a power cutoff circuit which controls cutoff/resumption of power supply to said communication circuit, said sensor circuit, and said control circuit.

8. The RFID tag according to claim 7,

wherein said power cutoff circuit includes:

a power switch connected to a power supply wiring of said communication circuit, said sensor circuit, and said control circuit; and

a timer circuit which controls ON/OFF of said power switch based on time.

9. An RFID reader/writer which generates a carrier signal for supplying power to RFID tags each incorporating a sensor circuit and is capable of wireless communication with said RFID tags,

wherein said RFID reader/write includes a function to stop generation of said carrier signal for a predetermined period during each intervals between measurements when said RFID tags perform the measurements successively several times by using said sensor circuit.

10. A processing method of an RFID system which includes RFID tags each having a communication circuit, a control circuit, and a sensor circuit integrated on one semiconductor chip, and an RFID reader/writer which generates a carrier signal to said RFID tags and is capable of wireless communication with said RFID tags, wherein measurements including a first measurement and a second measurement are performed several times by using said sensor circuit, said method comprising:

a first step of generating an instruction for performing said first measurement from said RFID reader/writer to said RFID tags;

a second step of performing said first measurement by said RFID tags;

a third step of stopping generation of said carrier signal from said RFID reader/writer to said RFID tags after an end of said first measurement;

a fourth step of resuming generation of said carrier signal from said RFID reader/writer to said RFID tags after a predetermined period elapses;

a fifth step of generating an instruction for performing said second measurement from said RFID reader/writer to said RFID tags; and

a sixth step of performing said second measurement by said RFID tags.

11. The processing method of an RFID system according to claim 10, further comprising:

before said first step,

a seventh step of transmitting a first setting required for said first measurement from said RFID reader/writer to said RFID tags;

an eighth step of storing said transmitted first setting in a non-volatile memory by said RFID tags; and

a ninth step of stopping generation of a carrier signal from said RFID reader/writer to said RFID tags for a predetermined period and then resuming the generation, and

between said fourth and fifth steps,

a tenth step of transmitting a second setting required for said second measurement from said RFID reader/writer to said RFID tags;

an eleventh step of storing said transmitted second setting in said non-volatile memory by said RFID tags; and

a twelfth step of stopping generation of a carrier signal from said RFID reader/writer to said RFID tags for a predetermined period and then resuming the generation.