Backscatter Temperature Sensing using Carbon Fibre Loaded Polymers and Inter-tag Channel Estimation

Abstract

We present a novel temperature sensing approach leveraging inter-tag channel estimation to allow wireless measurement. The approach decouples measurements from the reader to tag channel. A temperature-sensitive polydimethylsiloxane carbon-fibre (PDMS-CF) composite is integrated onto a split-ring resonator (SRR) positioned between two closely spaced tags comprising backscatter antennas. Under resonant conditions, the SRR suppresses the inter-tag channel. Heating alters the dielectric properties of the PDMS-CF, shifting the SRR resonance and producing measurable variations in the estimated inter-tag channel. We detail the design and implementation of the proposed system and validate its performance through both vector network analyser (VNA) and backscatter experiments. Experimental results demonstrate temperature-dependent resonant frequency shifts of 0.72 MHz per degree Celsius, and phase variations up to 4.4 degrees per degree Celsius across the 30–50 degree Celsius range, with good agreement between backscatter and VNA measurements. The results further consider the benefit of multi-frequency interrogation for extending the temperature sensing range. The proposed approach enables sensitive, zero-power temperature sensing without degrading tag performance, offering a scalable and robust solution for passive wireless sensing applications.