Inorganic, dielectric composite materials as sensitive elements for chipless wireless high temperature microwave RFID sensors
Synthesis and Properties of Functional Materials
Final Report Abstract
Most modern sensors rely on the powerful semiconductor technology so that the measured raw data can be preprocessed in the sensor itself for example. Though, when it comes to harsh environment monitoring tasks, it is hard to work with semiconductors. High temperatures, strong vibrations and fast accelerations could destroy the semiconductor materials and the bonding wires can tear off. One example for such a harsh environment sensing task is the temperature monitoring of a jet engine of an airplane. A direct temperature measurement of the hottest regions will enable improved monitoring capabilities so that a more efficient combustion process becomes possible. Moreover, potential malfunctions can be detected at an earlier point in time. Appropriate reactions can therefore prevent major damages to the system and possible emergency steps can be initiated earlier to even save human lives. A harsh environment temperature sensor can hardly rely on semiconductors nor on batteries or wiring. This is why there is a development towards passive chipless wireless sensors. The term passive indicates that such sensors basically work as reflectors and that they are read out via a passive backscatter scheme. Chipless means that no semiconductors are used and wireless implies that the readout is performed with radio frequency (RF) signals. The focus of this project lies on a robust RF temperature sensor based on a multilayer dielectric resonator design. When the temperature is increased, the dielectric constant changes. This will cause a shift of the resonance frequency of the resonator so that each temperature value has its own individual spectral signature. To perform the readout, a reader device transmits a broadband signal to the sensor. The backscattered and time gated signal reveals the resonance frequency and with that the temperature of the dielectric resonator. Different resonator sizes can be used to address multiple sensors in the same machine as each sensor will respond in its own frequency range. This work investigates the advantages of a multilayer resonator design with which the radiation properties can be influenced. This is necessary when highly lossy materials are used to increase the radar cross-section (RCS) of the dielectric resonator. A high RCS leads to an easier readout process and enables longer readout distances. While coherent layered composites could be made, the expected result in dielectric loss could not be achieved. Since the temperature sensitivity is decreased accordingly, the development of particulate composites is deemed superior to layered composites, as these either feature sources of dielectric loss that could not be identified or do not comply with the applied models. The successful development of the manufacturing process performed by the Karlsruhe Institute of Technology (KIT) as well as wireless high temperature measurements performed by the Institute for Microwave Engineering and Photonics (IMP) completed the first part of the project.
Publications
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“Chipless Wireless High Temperature Sensing Based on a Multilayer Dielectric Resonator”, 2019 IEEE Sensors, Montreal, CA, 2019, pp. 1-4
A. Jiménez Sàez, P. Schumacher, K. Häuser, M. Schüßler, J. R. Binder and R. Jakoby
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“Layered Ceramic Composite System for Application as Temperature Sensor”, 2019 XVI ECerS Conference, Turin
K. B. Haeuser, P. Schumacher, M. Schüßler, A. Jiménez-Sáez, R. Jakoby and J. R. Binder
