Placement of Multiple RFID Reader Antennas to Alleviate the Negative Effect of Tag Orientation

One primary issue which hinders large-scale Radio Frequency Identification (RFID) applications is the imperfect read rate. According to Friis equation and experiments, we find that the dipole tag´s orientation plays a significant role in read performance both in theory and practice. In this paper, we consider how to deploy multiple reader antennas to alleviate the negative effect caused by uncontrollable tag orientations in item-level applications. Different from previous work, we expand the candidate antenna positions from the portal to real three dimensional space and establish two estimation functions based on sphere coverage models under different polarized environment. Meanwhile, we provide an improved enumeration scheme with leaping and layering search strategies based on sphere quadtree (SQT) model to find optimized deployment.