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Difference between a SAW resonator and a SAW filter?

B

billcalley

Jan 1, 1970
0
Hi All,

What is the difference between a SAW resonator and a SAW filter? Are
they interchangeable? (I.E. Will a SAW resonator act as a filter; and
can a SAW filter be used as the frequency determining element in a
UHF/VHF oscillator?).

Thanks!

Bill
 
D

doug dwyer

Jan 1, 1970
0
A SAW delay line filter can be thought of as two antenna facing each
other that operate not in the electromagnetic domain but in the acoustic
domain.
Each "antenna" is an interdigitated transducer the bandwidth of the
transducer is a function of the length, i.e. number of interdigitated
transducer pairs.
The overall bandwidth will be that of the combination of the two
transducers.
Complications are that a simple transducer is bidirecional but more
modern transducers are unidirecional like yagi antennae.
If only one transducer is used and mirror gratings are placed in front
and behind then the lost bidirecional energy is reflected back and
forward i.e. you have a resonator.
Two transducers between the mirrors gives a 2 port resonator.
Resonators make low loss narrow band filters delay line filters can be
wide band the more loss the better shape and bandwidth.
 
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