Patent ID: 7944338

Claim:
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.