Wake Up Device for Communications System
The present invention teaches a communications system comprising a first communications device for receiving data and a wake up signal. The first communications device comprises an active mode of operation and a sleep mode of operation for reducing power consumption. Further, the system comprises means for switching the first communications device to and from sleep mode in response to receiving the wake up signal. Further, the system comprises a second communications device for transmitting data to the first device during its active mode, while transmitting the wake up signal to the first device during its sleep mode.
1 . A method of tracking inventory, the method comprising:
positioning an interrogator unit in a first region, the interrogator unit comprising one or more transceivers communicatively coupled to one or more antennas, the interrogator unit being configured to transmit radio frequency (RF) signals;
transmitting by the interrogator unit via at least one of the one or more transceivers a first RF signal;
receiving by a first RFID tag the first RF signal;
transitioning to a first mode by the first RFID tag when the first RFID tag determines the first RF signal is at a first frequency and a first data rate; and
transitioning to a second mode by the first RFID tag when the first RFID tag determines the first RF signal is at a second frequency and a second data rate, the first RFID tag remaining in the first mode until transitioning into the second mode upon receipt of the first RF signal at the second frequency and the second data rate, and the first RFID tag remaining in the second mode until transitioning into the first mode upon receipt of the first RF signal at the first frequency and the first data rate.
2 . The method of claim 1 , wherein the first frequency is substantially equivalent to the second frequency.
3 . The method of claim 1 , wherein the first RFID tag determines a frequency and a data rate of the first RF signal via one or more bandpass filters and one or more envelope detectors.
4 . The method of claim 1 , wherein the first RFID tag consumes less power in the first mode than the second mode.
5 . The method of claim 1 , wherein the first mode comprises operating states in which the first RFID tag requires more power than operating states of the second mode.