Novel high-resolution wireless temperature sensor based on sandwich complementary split-ring resonator substrate-integrated waveguide structure

Abstract 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 etched on the upper conductive layer of a printed circuit board (PCB) stack. This sandwich configuration integrates a temperature-sensitive CaTiO 3 dielectric core between two FR4 substrates ( ϵ r = 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 via a coaxial-to-waveguide converter. The compact sensor (36 mm × 36 mm × 3 mm) demonstrates stable operation over 25 °C–125 °C with 1.6 MHz °C −1 temperature-to-frequency resolution. The experimental results validate the design’s immunity to metallic interference while maintaining quadratic response characteristics ( R 2 = 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.