Metamaterial High–Temperature Sensor Based on All–Planar Substrate Integrated Waveguide

Extreme working environments with temperatures exceeding 800 °C often result in the failure of conventional sensors. Recently, ceramic–based microwave backscattering wireless passive high–temperature sensors have emerged as viable alternatives. Typically, waveguide transmission lines–integral components of these sensors–are fabricated on ceramic substrates using 3D manufacturing techniques such as drilling and metal backfilling. Nevertheless, tolerances in drilling and backfilling are unavoidable. These tolerances are further aggravated by non–reversible pore expansion at extremely high temperatures, may lead to sensor cracking or complete failure. In the present study, we introduce a metamaterial high–temperature sensor that utilizes an all–planar substrate–integrated waveguide. The sensor’s components are manufactured on alumina ceramic substrates exclusively through screen–printing, obviating the need for drilling. This approach effectively circumvents issues related to pore induced errors or failures and offers the advantages of ease of fabrication and cost–effectiveness. For sensing, a single square complementary split resonant ring (S–CSRR) serves as the metamaterial resonator, providing the requisite temperature sensitivity. In the antenna segment, a coplanar waveguide–fed monopole antenna with a bandwidth of 2.3 GHz is employed. Three types of metal slurry–Ag, PtRh10, and Pt–are utilized in sensor fabrication, rendering them suitable for maximum measurement temperatures of 800, 1200, and 1600 °C, respectively. The average temperature sensitivities for these three sensors are 236, 220, and 191kHz/°C, respectively. The proposed sensor, characterized by high integration, simplified processing, reduced fabrication costs, and a high Q–factor, holds significant application potential in industries such as aerospace, steel metallurgy, and energy mining.