Determining the Quality factor of resonator

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SUMMARY

The discussion focuses on determining the quality factor (Q) of a piezoelectric rectangular plate MEMS resonator using COMSOL Multiphysics 4.0a. The user is modeling mechanical oscillations and has successfully identified the desired eigenmode but struggles with calculating Q due to obtaining purely imaginary eigenvalues (λ), indicating an infinite Q. The user seeks guidance on defining damping parameters within the COMSOL environment to achieve accurate Q values for their specific geometry.

PREREQUISITES
  • Understanding of piezoelectric materials, specifically aluminium nitride.
  • Familiarity with COMSOL Multiphysics 4.0a and its modeling capabilities.
  • Knowledge of eigenvalue problems in mechanical oscillations.
  • Basic concepts of quality factor (Q) in resonators.
NEXT STEPS
  • Research how to define damping parameters in COMSOL Multiphysics for MEMS resonators.
  • Study the calculation of quality factor (Q) using eigenvalues in mechanical systems.
  • Explore advanced modeling techniques for contour mode resonators in COMSOL.
  • Investigate methods to interpret complex eigenvalues in the context of resonator performance.
USEFUL FOR

Engineers and researchers working on MEMS resonators, particularly those involved in piezoelectric applications and using COMSOL for simulation and modeling.

mohit21
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Respected members,
PLEASE help me in determining quality factor of a piezoelectric rectangular plate MEMS RESONATOR in COMSOL multiphysics.there is a need to define some 'damping'.where should i define that..
PLS HELP ME ITS URGENT
thank you and best
 
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mohit21 said:
Respected members,
PLEASE help me in determining quality factor of a piezoelectric rectangular plate MEMS RESONATOR in COMSOL multiphysics.there is a need to define some 'damping'.where should i define that..
PLS HELP ME ITS URGENT
thank you and best

Welcome to the PF.

How is the quality factor "Q" defined? How are you modelling the mechanical oscillations in COMSOL so far? Can you show us what you have done so far?
 
thanks for your quick reply

I am working on piezoelectric (aluminium nitride) vibrating contour mode resonators and filters.i am using COMSOL multyphysics 4.0a.
i have a rectangular plate geometry and i want to find contour mode that i got already.i got desired eigenmode(contour) at some eigenfrequency.
this is the thing i want to design (http://www.seas.upenn.edu/~piazza/Papers/Piazza_JMEMS_jan07.pdf
but i want to find Quality factor according to each eigenfrequency of desired mode.
i search in help there was a formula for Q. they r calculating Q by eigenvalue(lemda) as imaginary part divided by twice real part of lemda.thats ok
but i am getting purely imaginary lemda according to desired mode in comsol.means infinite Q
but it should be some definite value...

i am getting some complex lemdas also.which r not according to desired eigenmode.by formula Q will comes order of e-7 or lesser.

MEANS I DONT KNOW HOW TO FIND Q OF A GIVEN GEOMETRY ??
 
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