Patent ID: 8857725

Claim:
A radio frequency identification (RFID) door sensor system comprising: a door frame structure fixed in position; a door coupled to a portion of the door frame structure and configured to be oriented at a closed position with respect to the door frame structure and moveable to an open position with respect to the door frame structure; and an RFID device comprising: a near field only RFID tag fixed to one of the door and the door frame structure, wherein the near field only RFID tag in and of itself does not function as a far field RFID tag; a conductive element independent from the near field only RFID tag and fixed to another of the door and the door frame structure, the conductive element configured to function as a far field antenna; and wherein the near field only RFID tag and the conductive element are configured to be located in at least a first position and a second position relative to each other depending on a position of the door relative to the door frame structure; wherein the first position locates the near field only RFID tag and the conductive element relative to each other such that the conductive element is sufficiently decoupled from the near field only RFID tag in order that the RFID device only operates in a near field with respect to an RFID reader; and wherein the second position locates the near field only RFID tag and the conductive element relative to each other such that the conductive element is sufficiently coupled to the near field only RFID tag such that the RFID device operates in both the near field and a far field with respect to the RFID reader; wherein the first position exists when the door is in one of the open position and the closed position, and wherein the second position exists when the door is in the other of the open position and the closed position.