Self-steering RFID tags

A passive, self-steering RFID tag comprising:

• a first main antenna disposed in a central region of the tag;
• a second main antenna configured to receive an unmodulated wireless signal for powering a device;
• a power harvester configured to obtain power from the unmodulated wireless signal;
• a plurality of peripheral distributed antenna elements configured to direct a radiation pattern of the RFID tag;
• a main switch coupled to the power harvester and configured to activate selectively the passive RFID tag;
• a main circuit disposed in the central region and powered by the obtained power while in the active mode;
• and
• a control unit configured to automatically operate responsive to receiving input from a RFID reader and without receiving control information to:
• activate different combinations of the plurality of the peripheral distributed antenna elements, the different combinations includes a first combination and a second combination, the first combination including a first plurality of antennas and the second combination including a second plurality of antennas, the first plurality of antennas being different from the second plurality of antennas, and
• for each combination of the plurality of distributed antennas, to measure a signal strength at a location on the passive antenna device so that a signal strength of the first plurality of antennas is measured and a signal strength of the second plurality of antennas is measured;
• select the first combination in response to the first combination having a largest signal strength at the location on the passive antenna device compared with signal strengths of other combinations of the plurality of distributed antennas, including the second combination, at the location on the passive antenna device;
• and
• self-steer a radiation pattern of the passive antenna device by pointing a main beam of the passive antenna device in a direction of the RFID reader based on the selected combination of the plurality of distributed antennas.