HF RFID Card Optimization Regarding the IC’s Non-Linearity

Abstract:
The current state of the art optimization criterion for design of HF RFID cards bases on the choice of a resonance frequency and a quality factor. In this work, we demonstrate that these two parameters are necessary but not sufficient for the optimization process and their values do not reflect the main reason and conditions of full operation according to the standards. We show that the missing and most important parameter is the non-linearity introduced by the Integrated Circuit (IC) on the card, in addition to the dynamic range of the IC. Furthermore, we introduce the first optimization algorithm for such non-linear problem where the optimum coil’s inductance for a specific IC is systematically calculated. All results are verified using manufactured prototypes and standardized tests are carried out to verify the full compatibility of the card to the standard.