Optimization of the close coupling effect for passive UHF RFID tags in stacked applications

Abstract

The use of the radio frequency identification has become more popular in recent years, since it has many advantages (such as operation without human involvement or detection non-line-of sight at several meters) than the other identification system. The RFID tags are utilized in many different applications. In a wide range of applications (e.g. in the retail business), the RFID tags are often stacked together. The stacked UHF RFID tags are known to have less read range compare to the stand-alone tags. In the other words, placing the tag in the close proximity of other tags, affects the performance of the tag, due to electromagnetic interference between the antennas of the tags. The most of the analysis about effect of the close coupling have been done for the UHF RFID tags in near-field application. Since many different factors are involved in the performance of the tag in far-field applications, it is more complicated to analyze the interaction between the tags when they are placed in the close proximity of each other inside the far-field region of the reader antenna. In this project, the effect of some design parameters on the close coupling has been studied and one practical approach for improvement of the performance of the tags in the stacked application has been introduced. The performance of a reference tag in stack is measured. Then the new versions of the reference tag are designed by adjusting some of the reference tag antenna’s parameters. The measurement of the new version designs in stack shows the performance enhancement for one of the new design. The comparison between the results of the different designs verifies that the design parameters can have influence to the minimizing of the close coupling effect.