Re:  5. High Q resonator (hui li), Tuesday, April 08, 2003 7:49 AM

> One of the hot topics in RFMEMS is high frquency high Q rsonator. It seems

> that a high Q is of critical importance for MEMS resonators.
> However, i did not see any literature that specifies why a high Q is so
> important. Could anyone tell me why we need a such high Q?

High Q is important for all resonators used for frequency control, not only
RFMEMS.  For a tutorial on the subject (with notes and references below the
slides), see Chapters 3 and 4 at
http://www.ieee-uffc.org/freqcontrol/tutorials/vig/vig_tutorial1_files/frame
.htm
especially slides 76 to 78, and the section on noise in Chapter 4.

High Q is necessary (but not sufficient) for high stability.  Phase noise
close to the carrier, for example, varies as f^2/Q^2, so, the lower the Q,
the higher the noise.  For a quartz resonator, Qf = constant (the higher the
f, the lower the Q), so that phase noise close to the carrier varies as
Q^-4!

Lots of additional information can be found at the IEEE Frequency Control
website, www.ieee-uffc.org/fc, especially in the review papers, tutorials
and Digital Archives.  The Archives contain 100K pages of full-text papers
and ten books, many of which discuss Q and noise.  (You have to be an IEEE
UFFC-S member to access some of the info.)

........................John.


*********************************************
John R. Vig, Ph.D.
US Army CECOM RDEC
AMSEL-RD-C2-PT
Ft. Monmouth, NJ 07703-5602, USA

John.Vig@us.army.mil
732.427.4275
*********************************************