Printed polymer based RFID antenna on curvilinear surface

Rigid-flex RFID tags with the antenna and interconnections printed on low cost flexible substrate is a low cost route for RFID production. When these printed tags are affixed onto cylindrical containers, the RF performance is affected by the bending. The effects of bending on RFID performance are investigated in this study. Conductive polymeric coil antennas with different line thicknesses and designs were screen printed onto flexible substrates for use with 13.56 MHz RFID tags. The antenna coils were mounted on curved surfaces. S-parameters of the antenna coils were measured, and coil resistances and the inductances were delineated. RFID dies were mounted onto the antenna coils and the read ranges were characterized as a function of surface curvature. While the coil inductance decreased slowly with increasing curvature, the maximum read range of the tags was dramatically reduced. On the basis of the results, design guidelines are developed for printed RFID tags and implementation issues for printed antenna coils on curvilinear surfaces are discussed.