Multifrequency Impedance Characterization for Radio Frequency Identification Chip

This article introduces an innovative methodology for measuring the impedance of RFID (Radio Frequency Identification) chips. The primary objective is to develop a technique that enables impedance measurement across a range of frequencies, centered around the critical operational frequency of RFID systems, specifically 13.56 MHz. Unlike conventional methods, which typically focus solely on the impedance at 13.56 MHz, this approach utilizes the reflection coefficient of the device under test (DUT) to measure impedance over a broader frequency spectrum. This spectrum encompasses the frequencies within the ISO14443 communication bandwidth. The excitation signal is carefully selected to closely mimic an actual RFID communication frame. The experimental results demonstrate the feasibility of this method by comparing the impedance measurements of passive component pairs against those obtained using a vector network analyzer (VNA). Subsequently, the technique is applied to an RFID chip, underscoring its practical applicability and accuracy.