Patent ID: 8742896

Claim:
A method of locating and tracking an RFID tag, the steps comprising: calibrating at least two phase array steerable antennas to optimally align the antennas with known global coordinates; configuring an RFID reader for a working environment; performing a two-dimensional raster scan of a visible area of the working environment with a first antenna; calculating a minimal covering of the visible area with one or more beam areas; defining a set of steering directions for raster scans; using the first antenna to determine if one or more RFID tags are present in the beam areas; estimating an expected location for at least one RFID tag in the beam area; projecting the expected location of the RFID tag into global coordinates; estimating the most probable conjugate pairing (“PGPt 1 ”); calculating a most likely location of the RFID tag's projection in global coordinates relative to a second antenna (“PGPt 2 ”) using an estimated random distribution of RFID tag heights and PGPt 1 ; calculating a projection in global coordinates inverse of PGPt 2 so as to yield a most probable steering direction for the second antenna; reading with the other antenna in the direction indicated by a plane point projection of PGPt 2 ; triangulating any RFID tag seen by the other antenna using PGPt 1 and PGPt 2 ; triangulating using PGPt 1 and PGPt 2 if the RFID tag is not seen by the other antenna, as this location is still highly probable as a location for the RFID tag; and repeating these steps for each beam area.