Inorganic, dielectric composite materials as sensitive elements for chipless wireless high temperature microwave RFID sensors

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Temperature measurements are an essential part of the automatic control of industrial processes. Especially for the control and optimization of high temperature processes (e.g. combustion), measurement setups up to 1000 °C and beyond are required, and, therefore, a remote or wireless measurement is often beneficial or mandatory. Several possibilities exist to measure extremely high temperatures wirelessly, e.g. infrared thermometers or SAW temperature sensors. However, most of the approaches don't use a dedicated sensor element that resides in the hot environment, which would allow for more accuracy and non-line of sight operation, and approaches that do use a dedicated sensor element are limited either in operation duration or by a low maximum operation temperature. Chipless wireless sensor technology is a promising approach to solve these issues and provide sensors that even allow wireless readout through thick dielectric temperature shielding of furnaces. Especially the use of dielectric resonators (DR) has proven extremely reliable and versatile. However, the relationship of parameters for appropriate system layout are rather unknown to date, since research on this topic, inside and outside of the research team that proposes this project, is limited by available materials, and sensor and system optimization was hardly performed for the electromagnetic as well as for the material science part. Therefore, the task of the proposed project is the research on inorganic composites and new electromagnetic resonator structures to enable a high number of degrees of freedom for sensor system design.The central idea of the project is the design of DRs from layered dielectrics. A composition of high-Q (low loss), low permittivity materials without noticeable temperature dependence, and low-Q, high permittivity materials that are highly temperature dependent will lead to a broad range of different optimization directions, e.g. for broad temperature range sensors with moderate resolution or for highly accurate sensors in a narrow temperature window. First, the novel layered DR concept will be investigated at low temperatures with known materials. In a second step, the concept will be transferred to higher temperatures by the utilization of newly investigated materials. Eventually, both, temperature-independent and engineerable temperature-dependent materials are required to realize the RFID and the sensor part of a fully integrated RFID sensor tag.While the main application of such sensors serves as the general motivation, the layered DR approach can be utilized for the characterization of low-Q materials at extremely high temperatures, thus delivering a new characterization concept as well as first characterization data for the materials that are investigated for the sensor. Therefore, the investigation of a novel, model-based characterization method for dielectric parameters based on layered DRs is the another task of the project.