Tag communication device and tag communication method
First Claim
1. A tag communication device for performing wireless communication with an RFID tag by transmitting an interrogating wave from an antenna to a mobile object with the RFID tag attached in a predetermined communication range, the tag communication device comprising:
- Doppler measurement means for obtaining a Doppler signal for every frequency from transmission waves with a plurality of frequencies and reflected waves thereof;
phase difference detection means for detecting a phase difference of the Doppler signals of two frequencies of the Doppler signals for every frequency; and
communication control means for controlling the transmission of the interrogating wave so as to transmit the interrogating wave when the phase difference is detected by the phase difference detection means, and so as not to transmit the interrogating wave when the phase difference is not detected by the phase difference detection means.
1 Assignment
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Accused Products
Abstract
To improve communication between tags by causing a mobile object having a RFID tag attached to transmit an interrogating wave only when moving in a communication range to reduce power consumption and prevent occurrence of tag confusion. By acquiring two Doppler signals from 2-frequency transmission waves (CW) with different frequencies and respective reflected waves and detecting phase difference from the Doppler signals, a cargo (21A) is detected to be moving in the communication range (A). Only when the movement is detected, a reader-writer (1A) transmits the interrogating wave (RW).
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Citations
18 Claims
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1. A tag communication device for performing wireless communication with an RFID tag by transmitting an interrogating wave from an antenna to a mobile object with the RFID tag attached in a predetermined communication range, the tag communication device comprising:
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Doppler measurement means for obtaining a Doppler signal for every frequency from transmission waves with a plurality of frequencies and reflected waves thereof; phase difference detection means for detecting a phase difference of the Doppler signals of two frequencies of the Doppler signals for every frequency; and communication control means for controlling the transmission of the interrogating wave so as to transmit the interrogating wave when the phase difference is detected by the phase difference detection means, and so as not to transmit the interrogating wave when the phase difference is not detected by the phase difference detection means. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A tag communication device for performing wireless communication with an RFID tag by transmitting an interrogating wave from an antenna to a mobile object with the RFID tag attached in a predetermined communication range, the tag communication device comprising:
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first Doppler measurement means for obtaining a first Doppler signal from a transmission wave with a first frequency and a reflected wave thereof; second Doppler measurement means for obtaining a second Doppler signal from a transmission wave with a second frequency different from the first frequency and a reflected wave thereof; phase difference detection means for detecting a phase difference between the first Doppler signal and the second Doppler signal; and communication control means for controlling the transmission of the interrogating wave so as to transmit the interrogating wave when the phase difference is detected by the phase difference detection means, and so as not to transmit the interrogating wave when the phase difference is not detected by the phase difference detection means.
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10. A tag communication method for performing wireless communication with an RFID tag by transmitting an interrogating wave from an antenna to a mobile object with the RFID tag attached in a predetermined communication range, the tag communication method comprising the steps of:
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a Doppler measurement step for obtaining a Doppler signal for every frequency from transmission waves with a plurality of frequencies and reflected waves thereof; a phase difference detection step for detecting a phase difference of the Doppler signals of two frequencies of the Doppler signals for every frequency; and communication control step for controlling the transmission of the interrogating wave so as to transmit the interrogating wave when the phase difference is detected by the phase difference detection step, and so as not to transmit the interrogating wave when the phase difference is not detected by the phase difference detection step. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17)
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18. A tag communication method for performing wireless communication with an RFID tag by transmitting an interrogating wave from an antenna to a mobile object with the RFID tag attached in a predetermined communication range, the tag communication method comprising the steps of:
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a first Doppler measurement step for obtaining a first Doppler signal from a transmission wave with a first frequency and a reflected wave thereof; a second Doppler measurement step for obtaining a second Doppler signal from a transmission wave with a second frequency different from the first frequency and a reflected wave thereof; a phase difference detection step for detecting a phase difference between the first Doppler signal and the second Doppler signal; and a communication control step for controlling the transmission of the interrogating wave so as to transmit the interrogating wave when the phase difference is detected by the phase difference detection step, and so as not to transmit the interrogating wave when the phase difference is not detected by the phase difference detection step.
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Specification