Method and apparatus for localization of RFID tags

摘要

A method and apparatus for an RFID tag to facilitate the determination of its location while at the same time minimizing the energy drain on the tag's battery. At predetermined intervals, the tag transmits its identifier along with status information. If the status indicates that the tag is in a new location, the tag will then expend additional battery energy by participating in the determination of its location. The distance from an interrogator to the tag is determined by transmitting two signals from the interrogator that propagate at different velocities. By determining the difference in arrival times at the tag of the two signals, the distance from the interrogator to the tag can be determined.

主权项

1. An RFID tag capable of assisting in a determination of its location, comprising:
a timer to periodically generate a signal at a predetermined time interval; a controller to be powered up upon receiving the periodically generated signal from the timer; a radio frequency (RF) transceiver to send an identifier associated with the RFID tag at the predetermined time interval from the RFID tag in response to the powering of the controller by the periodically generated signal from the timer; a motion sensor to determine whether the RFID tag has been moved to a different position, wherein to determine whether the RFID tag has been moved comprises:
receiving a first indication of movement from the motion sensor;receiving a time interval signal measured according to the first indication of movement;receiving a second indication that movement is occurring;receiving a third indication that movement has not occurred for a predetermined time period; anddetermining that the RFID tag has ceased movement according to the second indication that movement is occurring and the third indication that movement has not occurred for the predetermined time period; and an ultrasound receiver to receive signals traveling at a second velocity compared with a first velocity of signals received by the transceiver that determines a location of the RFID tag in a new position responsive to the motion sensor.