PROOF OF CONCEPT DESIGN FOR PRECISE SINGLE DIMENSION POSITION DETERMINATION USING PASSIVE RFID

Position determination in RFID systems is a very useful aspect in tracking and managing items, to which a tag device is attached. Knowing the precise location of an item, relative to its environment, allows accurate mapping and control of the item with respect to those people, or things, that use the item's services. Current methods employ zone based localization, triangulation, or tag response time calculation. These methods are not very accurate, and are all reader side solutions. A tag side solution has been developed at the University of Pittsburgh to precisely determine the position of a tag, or reader, using passive RFID technology. Using the electromagnetic field intensity created by a reader, a tag that passes through this field will experience more excitation when parallel to and at the center of the field. Translating this action into DC voltage, a bell shaped voltage curve is apparent. Identifying the peak of this curve, therefore, directly relates to identifying the moment when the tag and reader are parallel and centered. Transmission of an ID, or location, at that moment, then, precisely describes its position. With the described motion in a known, single dimension, the item can be controlled to an even greater degree. One application is that of unmanned transit control. Using multiple tags, a transit car can be slowed and precisely stopped at an approaching station platform. The research contained within proves the existence of the voltage peak, develops an algorithm to find the peak, and creates a tag that can transmit the position ID using harvested RF energy