Summary:

SAWs (Surface Acoustic Waves) are devices widely used as filtering components in telecommunications. They are typically composed of a resonant acoustic cavity, one or more electroacoustic transducers and two mirrors. The operating frequency of such a device depends on numerous parameters, including the material used for the substrate, the geometry of the transducer(s), the geometry of the mirrors and the interaction between the various elements. In order to achieve the best possible response, criteria are established for each of the elements making up the resonator. SAWs have a spectral (or frequency) response determined during their design and manufacture. The idea of bringing frequency agility to these components is an important one, in terms of cost and reducing the volume footprint of filtering devices. When several frequency bands are addressed by a single device, each band is processed by a specific SAW component, which increases the volume occupied and the cost. However, recent research has shown that by modifying the electrical conditions of the mirrors, it is possible to change the operating frequency of the resonator without changing the device and preserving the integrity of the filtering function. The applications linked to this phenomenon have led to the filing of a Thales TRT/CNRS patent, Frec'n'sys, thanks to a joint project between the various partners. In the longer term, the potential applications of this concept concern the use of a single device to investigate several frequency bands for the same filtering function. The aim of the thesis is to go a step further in analysing the phenomena highlighted and exploiting them to design new agile filtering components for telecommunications applications. Using the design tools, the implementation of optimisation algorithms, based on genetic algorithms for example, will make it possible to propose agile configurations that meet precise objective criteria. Some components will be selected on the basis of frequency agility criteria. The component design, characterisation and agility testing phase is planned. A particular focus will be on agile electronic controls.

Abstract:

SAWs (Surface Acoustic Waves) are devices widely used as filtering components in the telecommunications field. They are typically composed of a resonant acoustic cavity, one or more electroacoustic transducers and two mirrors. The operating frequency of such a device depends on many parameters including the material used for the substrate, the geometry of the transducer(s), the geometry of the mirrors and the interaction between the various elements. In order to have the best possible response, criteria are established for each of the elements composing the resonator. SAWs have a spectral (or frequency) response determined during their design and manufacture. The idea of bringing frequency agility to these components is important, both in terms of cost and in terms of reducing the volume footprint of the filtering devices. When several frequency bands are addressed on a single device, each band is processed by a specific SAW component which implies an increase in the occupied volume and cost. However, recent research has shown that by modifying the electrical conditions of the mirrors, the operating frequency of the resonator can be changed without changing the device and preserving the integrity of the filtering function. The applications related to this phenomenon have led to the filing of a Thales TRT/CNRS patent, Frec'n'sys, thanks to a joint project between the different partners. In the longer term, the potential applications of this concept concern the use of a single device to investigate several frequency bands for the same filtering functionality. The goal of the thesis is to go further in the analysis of the highlighted phenomena and their exploitation to design new agile components for filtering for telecommunication applications. From the design tools, the implementation of optimization algorithms, from genetic algorithms for example, will allow to propose agile configurations, answering precise objective criteria. Some components will be selected according to frequency agility criteria. The phase of realization, characterization and test in agility of the components is planned. A particular focus will be on agile electronic controls.