Alok POKHAREL : "Analysis by "reverse engineering" methods of ultra-table piezoelectric resonators and noise modeling

Alok POKHARELPhD Works  : "Analysis by "reverse engineering" methods of ultra-table piezoelectric resonators and noise modeling"

The thesis dissertation is public and everyone is compulsorily requested to attend the dissertation with their masks on (no masks are provided on the venue) and maintain a proper social distancing while being seated inside the Amphitheatre

Abstract : Bulk Acoustic Wave Resonators (BAW) have been studied in Time and Frequency domain for a long time,particularly at FEMTO-ST. They have an essential role in many metrological applications such as in positioning devices like GPS, Glonass, Galileo, etc. This thesis work presents the passive technic used for phase noise
measurement in high-performance BAW resonators. These resonators were fabricated by several European manufacturers and provided for the thesis work by CNES for reverse engineering investigations. The work begins with recalling the basics of piezoelectricity in quartz and noise in ultra-stable resonators. The second part of the
work gives details on noise measurement by carrier suppression technic with an alternative technic for low impedance resonators (< 10 ohms). The third part is about the comparison of Steven-Tiersten’s model with our phase noise measurement results at different temperatures and classification of resonators according to their short-term stability. A finite element simulation is used to compare the theory and experimental results. The fourthpart presents tests using Mittag-Leffler distribution and stable distributions of a model of phase noise due to power law intermittency. Finally, the “reverse engineering” work is carried out by dismantling some resonators for
defects analysis using X-rays diffraction and laser scattering. This revealed macroscopic imperfections and a few dislocations which could be a possible cause for phase noise in the resonators. This will have to be confirmed and quantified with other resonators.

Jury composition :

M. Fabrice STHAL, Professeur des Universités, ENSMM, Phd Director
M. Olivier LLOPIS, Directeur de recherche, LAAS-CNRS, Reporter
M. Sergio CILIBERTO, Directeur de recherche, Laboratoire de Physique de ENSL, Reporteur
M. Michel PRIGENT, Professeur des Universités, IUT du Limousin - Dept GEII, Reviewer
M. Nicolas VOROBYEV, Ingénieur, CNES, Reviewer
M. Michel DEVEL, Professeur des Universités, ENSMM, Reviewer
M. Joël IMBAUD, Maître de conférences, Institut FEMTO-ST, ENSMM, Phd Co-director

Localization : Amphithéâtre Pierre Mesnage, ENSSM, 26, rue de l’Epitaphe, Besançon