Large-Area Electronics HF RFID Reader Array for Object-Detecting Smart Surfaces

This letter presents a system that enables identification and localization of objects through an array of RFID-readers integrated into a thin sheet via large-area electronics, for lining everyday surfaces. We demonstrate a 5 × 5 active matrix of RFID readers based on thin-hlm transistor (TFT) LC oscillators, using in-house fabricated ZnO TFTs. The array is designed to read commercial ISO14443 13.56 MHz tags, employing a tag-talks-hrst protocol to maximize readout speed for high array frame rate. The spatial resolution is set by the reader coil dimensions, which are 3.7 cm × 3.7 cm, for a maximum of 730 pixels/m2. Using a 2.4 cm × 2.4 cm tag the array achieves a vertical read range of 3 cm and lateral range of 1.6 cm at a readout speed of 5 ms per element (set by the commercial tag). Readout is accomplished by sensing the current via the shared VDD line of the array, in order to reduce interfacing requirements as array size scales. After hltering and amplihcation, the demodulated data has an amplitude of . 350 mV and the maximum power consumed by the reader array is . 280 mW.