The new communication standards allow to improve communication speeds, and the strategy adopted is to go higher and higher in frequency. In particular, with the arrival of 5G, several frequency bands are envisaged from GHz to the hundreds of GHz. For the characterization of materials, these new bands constitute a field of study still unexplored. At the same time, we are witnessing the rise of the Internet of Things (IoT), whose technological developments are based on the mass use of sensors that can be integrated into each object, which is then referred to as the connected object or the Internet of Things (IoT). Except that integrating these sensors on objects requires extreme compactness and adaptability to all types of shapes and materials. The increase in frequency allows us to study miniaturized and flexible sensors of reduced size. In this thesis, we are interested in the characterization of thin film bio-polymers, which present a complex permittivity depending on the climatic conditions [1] and the gas concentration. These bio-polymers can be used as sensitive materials for the realization of wireless sensors as we have demonstrated with the thesis of Yassin Belaizi [2], and Benjamin Saggin [3] in the framework of the H2020 Glopack project at UHF frequencies, with RFID devices. We now have complex permittivity data below GHz and wish to extend these characterizations to 60GHz. Moving from centimeters to millimeters will allow us to obtain smaller structures but also more sensitive for sensor applications (climatic data, pollution...). Indeed, the use of waveguides or cavities becomes possible and the skin thickness of the conductive materials is less than µm. A sensitive film deposited in a thin layer will therefore have more impact than at centimetric wavelengths. Several methods will be implemented to perform the largest possible material characterization:
- Measurement by planar and inter-digital capacitance at frequencies 0Hz-100MHz
- Measurement by coaxial probe, planar transmission lines and cavity at frequencies 100MHz-20GHz
- Measurement by reflectometry and wireless transmission at millimeter frequencies > 20GHz
The first part of the thesis will focus on the state of the art on the characterization methods of dielectric materials from 0Hz to 60GHz as well as on the sensitive bio-polymers. Among these bio-polymers, we are particularly interested in wheat gluten which we have already studied at frequencies < 1GHz.
The second part of the thesis will consist in setting up/designing test benches for the broadband characterization of dielectric materials. The difficulty will be to integrate the control of the environment around the sensitive device in terms of temperature, humidity, and gas concentration without affecting the electromagnetic response of the material under test. We will then perform a multi-frequency characterization campaign, varying the environmental parameters around the sensitive element.
In the last part of the thesis, we will first identify the sensor structures that can be designed in millimeter bands in order to improve the sensitivities. Then the study of novel design of RF sensors will be performed. Waveguide structures with a bio-polymer film on the walls, or resonators and waveguides integrated on substrates (SIW) [4] will be studied. The sensor information will have to be read with a wireless technology by reflectometry [5].
[1] F. Bibi, C. Guillaume, A. Vena, N. Gontard, B. Sorli, “Wheat gluten, a bio-polymer layer to monitor relative humidity in food packaging: Electric and dielectric characterization,” Sensors and Actuators A: Physical, 247, 355-367, 2016
[2] Y. Belaizi, A. Vena, B. Sorli, And F. Bibi, “A Biopolymer-based UHF RFID Sensor for Humidity Monitoring,” 32nd URSI GASS, Montreal, August 2017
[3] B. SAGGIN, Y. Belaizi, A. Vena, B. Sorli, V. Guillard and I. Dedieu, "A Flexible Biopolymer based UHF RFID-Sensor for food quality monitoring," 2019 IEEE International Conference on RFID Technology and Applications (RFID-TA), Pisa, Italy, 2019, pp. 484-487, doi: 10.1109/RFID-TA.2019.8892248.
[4] M. M. Usman, and S. Lim. “Microwave Chemical Sensor Using Substrate-Integrated-Waveguide Cavity [corrected].” Sensors (Basel, Switzerland) vol. 16,11 1829. 31 Oct. 2016, doi:10.3390/s16111829
[5] J. Li, T. Djerafi, F. Ren and K. Wu, “Chipless Substrate Integrated Waveguide Tag Using Time-Domain Reflectometry Technique for Millimeter-Wave Identification (MMID)”, EUCAP 6016, pp.1-3.
Funding category: Contrat doctoral
PHD Country: France