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

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 frequency. The proposed method is verified by simulations and by comparing measurement results with the state-of-the-art. The results show that the proposed method offers significant advantages over the state-of-the-art method.