Novel High Resolution Wireless Temperature Sensor based on Sandwich CSRR-SIW Structure

This paper presents a novel high-resolution wireless temperature sensor based on microwave backscattering principles. The proposed design features a sandwich substrate-integrated waveguide (SIW) structure that incorporates a complementary split-ring resonator (CSRR) etched on the upper conductive layer of the PCB stack. This sandwich configuration integrates a temperature-sensitive CaTiO₃ dielectric core between two FR4 substrates (εᵣ=4.2), enabling enhanced electromagnetic field confinement and thermal-frequency transduction. The sensor was fabricated using standard PCB processing techniques. For experimental characterization, the fabricated device was placed on a heating plate and interrogated wirelessly through a rectangular waveguide antenna connected to a vector network analyzer (VNA) via a coaxial-to-waveguide converter. The compact sensor (36mm×36mm×3mm) demonstrates stable operation over 25-125°C with 1.6 MHz/°C temperature-to-frequency resolution. Experimental results validate the design's immunity to metallic interference while maintaining quadratic response characteristics (R²= 0.999935) across the operational range. This study demonstrates the feasibility of the sandwich SIW sensor and its broad application prospects for wireless temperature measuring.