Capteurs passifs à transduction électromagnétique pour la mesure sans fil de la pression

Mohamed Mehdi Jatlaoui 1
1 LAAS-MINC - Équipe MIcro et Nanosystèmes pour les Communications sans fil
LAAS - Laboratoire d'analyse et d'architecture des systèmes
Abstract : In the last years, there has been a proliferation of autonomous wireless sensors (pressure, acceleration, temperature) based on the availability of sensitive and efficient transducers, and secondly on new low cost electronic communication devices between 300MHz and 3GHz. These devices meet the growing demand for communicating sensors network for autonomous monitoring of distributed applications, analysis or diagnosis. However, the development of Wireless sensor networks communications has highlighted an inherent limitation of the use of most existing measurement cells related to energy autonomy of the system. Most research aimed at increasing the autonomy of sensors focus firstly on reducing the consumption of sensitive cells and electronic circuits and secondly on the availability of embedded energy. Although attractive, these potential solutions have major drawbacks such as complexity of devices implementation and low-current or unimportant quantity of stored energy. As part of this work, we became interested in the particular case of pressure sensors and we adopted a different approach. Indeed, the objective of this work is to rethink the working principle of the sensor by developing a completely new mode of passive transduction that do not require onboard power and can be interrogated at a great distance (several meters to tens meters) by radar. This mode called "electromagnetic transduction" is based on changing the resonant frequency of a microwave resonator by the measurand. This unusual method of transduction converts the effect of a pressure gradient in a frequency shift. In a first step, a theoretical validation, using an electromagnetic modeling, of the operating principle is presented. Then, the design of the measuring cell is highlighted, taking into account firstly the electromagnetic aspect related to the resonant circuit, and secondly the mechanical aspect relating to technological constraints for structures with silicon membrane. Subsequent ly, simulations and simplified electromagnetic simulations taking into account the actual deformation of the membrane were carried out to validate, through simulation, the frequency shift and thus validate the operating principle of the sensor. The next step identified the technological processes in clean rooms that have achieved the first sensor prototypes. Once the measuring cells manufactured, RF measurements were carried out and confirm the results of simulations. Then, using a test bench specially dedicated to this type of sensors, RF measurements combined with pressure measurements were conducted for the characterization of prototypes and for the sensitivity extraction. Finally, future directions are discussed concerning the wireless aspects and the sensor radar interrogation.
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Mohamed Mehdi Jatlaoui. Capteurs passifs à transduction électromagnétique pour la mesure sans fil de la pression. Micro et nanotechnologies/Microélectronique. Institut National Polytechnique de Toulouse - INPT, 2009. Français. ⟨tel-00559628⟩

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