Etienne VAILLANT "Contribution to the measurement of the sound of MEMS resonators"

This thesis work, supervised by the FEMTO-ST Institutre and co-financed by CNES and the France-Comté region, aimed at producing phase noise measurement systems covering three decades of frequencies, between 5 MHz and 5 GHz, as well as measuring the noise of MEMS resonators.
The phase noise of radio-frequency and microwave components is a classic problem in the time-frequency domain. However, some of the mechanisms behind the generation of this noise are still poorly known or even controversial. This is the case of the own noise of piezoelectric or mechanical resonators. However, when the amplifying electronics of the oscillating circuit is very optimized, the noise of these components represents the ultimate noise of the frequency source. It is therefore essential to study it in detail.
The work of this thesis deals with this problem mainly from the metrological angle. Much of this work has involved the development and improvement of phase noise measurement systems capable of accounting for the behavior of these components. Two measurement systems based on the interferometric technique were realized and allowed to measure devices between 5 MHz and 5 GHz. Among the measured MEMS resonators are surface wave resonators (SAWs), contour mode resonators (CMRs) and high harmonic mode volume wave resonators (HBARs).

 

In the case where it is not possible to simultaneously test two identical resonators, the use of sources with very low phase noise is necessary, like the cryogenic sapphire oscillators available at the TF department. The problem with these sources is that they deliver a signal in the microwave range and that their use in the RF range requires noise-optimized frequency division electronics. Thus, part of this PhD work is devoted to low-phase noise frequency synthesis, more particularly to the realization and characterization of integer or fractional order regenerative frequency dividers. State-of-the-art regenerative dividers have been made for a frequency of 20 MHz and a double-loop frequency divider architecture has been investigated to provide fractional fractional ratio.

Location : Amphithéâtre P. Mesnage -  ENSMM - 26, Rue de l'Epitaphe - Besançon