A precise resonance frequency measurement method based on ISO-standardized setups for contactless chip cards

Abstract

Abstract A method for measuring the resonance frequency of contactless chip cards is proposed in this article. Compared to the vector network analyzer (VNA) based state-of-the-art method, the method gives a more accurate definition of resonance frequency, removes the subjectivity associated with the state-of-the-art method, and makes the measurement integrable into ISO-standardized test setups. Signal processing and system modeling are applied in order to determine the maximum active power in the chip card over a chosen frequency range. This is achieved by using a transfer function obtained from the model and by setting a chirp signal as input to the system. The determined maximum of active power is mapped to the corresponding frequency in the chirp signal, which is defined as the resonance fre-quency. The proposed method is verified by simulations and by comparing mea-surement results with the state-of-the-art. The results show that the proposed method offers significant advantages over the state-of-the-art method.