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

• US 7,944,338 B2
• Filed: 07/25/2006
• Issued: 05/17/2011
• Est. Priority Date: 10/19/2005
• Status: Expired due to Fees

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Yazawa, Yoshiaki, Nemoto, Ryo, Yoshigi, Hiroshi, Watanabe, Kazuki
• Primary Examiner(s): Goins; Davetta W
• Assistant Examiner(s): GIRMA, FEKADESELASS
• Application Number:
  US11/491,990
• Publication Number:
  US 20070176772A1
• Time in Patent Office: 1,757 Days
• Field of Search: None
• US Class Current: 340/10.34
• 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 for wireless communication with said RFID tags by generating a carrier wave,

wherein said RFID reader/writer includes a function to cut off power supply to the internal circuits of said RFID tags by stopping generation of said carrier wave for a first predetermined period between confirmation of an ID of said RFID tags and a beginning of a measurement operation by using said sensor circuit,

the measurement operation includes successive measurements, and

the RFID reader/writer has a function to stop the generation of said carrier wave for a second predetermined period between each of the successive measurements,

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

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, and

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

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

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,

wherein each of said RFID tags having a power supply cutoff circuit for controlling cutoff/resumption of power supply to the internal circuits of said RFID tags, and

wherein each measurement operation includes a first processing step of performing various processes before execution of a 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 at least one of 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 measurements performed several times in said second processing step, and then calculate one measurement result for said second processing step.

2. 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 for wireless communication with said RFID tags by generating a carrier wave,

wherein said RFID reader/writer includes a function to cut off power supply to the internal circuits of said RFID tags by stopping generation of said carrier wave for a first predetermined period between confirmation of an ID of said RFID tags and a beginning of a measurement operation by using said sensor circuit,

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,

wherein each of said RFID tags having a power supply cutoff circuit for controlling cutoff/resumption of power supply to the internal circuits of said RFID tags, and

wherein each measurement operation includes a first processing step of performing various processes before execution of a 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 at least one of 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 measurements performed several times in said second processing step, and then calculate one measurement result for said second processing step.