Placement of multiple RFID reader antennas to maximise portal read accuracy

A critical factor in the adoption of Radio Frequency Identification (RFID) technology is the level of read accuracy that is achieved. With passive tags, the read accuracy depends on the volume of the region that receives sufficient power from the reader. Most current research considers the powering region of a reader to be determined only by its read range (i.e. distance). However, read accuracy also depends on the relative orientations of reader and tag antennas and their polarisations. In particular, when tag positions are not fixed, the locations of reader antennas relative to the tags can have a significant effect on the success of the interrogation processes. This paper uses Friis' equation to explicitly consider orientations and polarisations while addressing the problem of determining the best locations for a set of reader antennas at a scanning portal. The objective is to maximise the size of the powering region in order to maximise read accuracy. A methodology for determining the powering region with multiple antennas is developed along with an enumeration approach to determine optimal antenna locations.