Low-cost and low-profile near field UHF RFID transponder for tagging batteries and other metal objects

A new UHF RFID transponder solution especially designed for tagging batteries of portable devices is presented. The new transponder is a thin and low-cost label that can be read from the opposite side of the tagged object. This feature is based on utilizing the secondary currents induced on the metal object. The new transponder was first analyzed and optimized by electromagnetic simulations, and subsequently a small series of prototypes was fabricated. After finding the right dimensions by electrical measurements, a bigger series with the selected dimensioning was fabricated. With these prototypes a practical test of automatic sorting of batteries was run and the performance of the transponder in practice was evaluated by the yield of the test. In the test, yields of over 96 % were obtained, even though the reader setup was not optimized.