Spiral-Coupled-Line Resonators for Chipless RFID Sensors

This paper presents a chipless RFID sensor tag that support sensing parameters such as temperature. A new spiral-coupled-line structure is proposed to simultaneously support two state identification data (1bit) and extra sensing information. The proposed structure comprises a coupled line spiral resonator for identification and an extra arm connected to the spiral at an appropriate location to avoid loading effect. This line is covered by polyamide Stany 1 material that is very sensitive to the temperature. The spiral resonator has resonance frequency $f_{i}$ (logic 1 state) and can be disconnected near the intersection with the extra arm to shift its resonance frequency beyond the tag operation (logic 0 state). The extra arm connected all the time for temperature sensing and has resonance frequency f2. The change in tag temperature changes directly f2. A multi-resonator structure with six resonators is designed and simulated for RFID tags applications.