Hi Indrajit,

I assume you are working on distributed transmission line phase shifters
with periodic adjustable discrete capacitive air-bridge loading
(similar to those by Scott Barker et al) rather than switched delay line
phase shifters. If you do not have periodic loading, you will not have a
Bragg frequency.

The Bragg frequency is the frequency at which the individual reflections
from each of the periodically spaced air-bridges add up in phase
to maximize the reflection. This occurs at a frequency near the frequency
where the spacing between the capacitors is 1/4 of a wavelength on the
transmission line. It is not exactly 1/4 wave because of the capacitive
loading and the shunt inductance of the air-bridges.

Chapter 10 of Gabriel Rebeiz's book (pub by Wiley) covers this
type of phase shifter in detail or you can look back directly to Scott
Barker's papers.

Best Regards,

Art

Arthur S. Morris III, Ph.D.              art.morris@wispry.com
CTO, VP Eng.                             v: 1-919-657-8101
wiSpry, Inc.                             f: 1-919-854-7501
4001 Weston Parkway, Suite 200           http://www.wispry.com/
Cary, NC 27513

>
>
> >
> > ------------------------------
> >
> > Message: 2
> > Date: Wed, 24 Dec 2003 23:52:59 +0530 (IST)
> > From: "Mr. Indrajit Paul" 
> > Subject: [mems-talk] bragg frequency(RF MEMS)
> >
> > Hello everyone
> >   I am working on RF MEMS based phase shifters, in almost all the
> > publications there is a mention of bragg frequency which limits the
> > operation range of the device. However i am yet to get a single paper
> > where proper derviation/ implications of this Bragg frequency is
> > mentioned.
> >  I would be thankful if anyone can help me in this regard. I
> want details
> > on bragg frequency .
> > Thanks in advance
> > Indrajit
> >
>
>