<s>
A	O
crystal	B-Algorithm
filter	I-Algorithm
allows	O
some	O
frequencies	O
to	O
'	O
pass	O
 '	O
through	O
an	O
electrical	O
circuit	O
while	O
attenuating	O
undesired	O
frequencies	O
.	O
</s>
<s>
An	O
electronic	B-Architecture
filter	I-Architecture
can	O
use	O
quartz	B-General_Concept
crystals	O
as	O
resonator	O
components	O
of	O
a	O
filter	O
circuit	O
.	O
</s>
<s>
Quartz	B-General_Concept
crystals	O
are	O
piezoelectric	O
,	O
so	O
their	O
mechanical	O
characteristics	O
can	O
affect	O
electronic	O
circuits	O
(	O
see	O
mechanical	O
filter	O
)	O
.	O
</s>
<s>
In	O
particular	O
,	O
quartz	B-General_Concept
crystals	O
can	O
exhibit	O
mechanical	O
resonances	O
with	O
a	O
very	O
high	O
Q	O
factor	O
(	O
from	O
10,000	O
to	O
100,000	O
and	O
greater	O
far	O
higher	O
than	O
conventional	O
resonators	O
built	O
from	O
inductors	O
and	O
capacitors	O
)	O
.	O
</s>
<s>
The	O
crystal	O
's	O
stability	O
and	O
its	O
high	O
Q	O
factor	O
allow	O
crystal	B-Algorithm
filters	I-Algorithm
to	O
have	O
precise	O
center	O
frequencies	O
and	O
steep	O
band-pass	O
characteristics	O
.	O
</s>
<s>
Typical	O
crystal	B-Algorithm
filter	I-Algorithm
attenuation	O
in	O
the	O
band-pass	O
is	O
approximately	O
2-3dB	O
.	O
</s>
<s>
Crystal	B-Algorithm
filters	I-Algorithm
are	O
commonly	O
used	O
in	O
communication	O
devices	O
such	O
as	O
radio	O
receivers	O
.	O
</s>
<s>
Crystal	B-Algorithm
filters	I-Algorithm
are	O
used	O
in	O
the	O
intermediate	O
frequency	O
(	O
IF	O
)	O
stages	O
of	O
high-quality	O
radio	O
receivers	O
.	O
</s>
<s>
The	O
most	O
common	O
use	O
of	O
crystal	B-Algorithm
filters	I-Algorithm
are	O
at	O
frequencies	O
of	O
9MHz	O
or	O
10.7MHz	O
to	O
provide	O
selectivity	O
in	O
communications	O
receivers	O
,	O
or	O
at	O
higher	O
frequencies	O
as	O
a	O
roofing	B-Algorithm
filter	I-Algorithm
in	O
receivers	O
using	O
up-conversion	O
.	O
</s>
<s>
The	O
vibrating	O
frequencies	O
of	O
the	O
crystal	O
are	O
determined	O
by	O
its	O
"	O
cut	O
"	O
(	O
physical	O
shape	O
)	O
,	O
such	O
as	O
the	O
common	O
AT	O
cut	O
used	O
for	O
crystal	B-Algorithm
filters	I-Algorithm
designed	O
for	O
radio	O
communications	O
.	O
</s>
<s>
The	O
cut	O
also	O
determines	O
some	O
temperature	O
characteristics	O
,	O
which	O
affect	O
the	O
stability	O
of	O
the	O
resonant	O
frequency	O
,	O
though	O
as	O
quartz	B-General_Concept
has	O
an	O
inherently	O
high	O
temperature	O
stability	O
,	O
its	O
shape	O
does	O
not	O
change	O
much	O
with	O
temperatures	O
found	O
in	O
typical	O
radios	O
.	O
</s>
<s>
Ceramic	O
filters	O
at	O
455kHz	O
can	O
achieve	O
similar	O
narrow	O
bandwidths	O
to	O
crystal	B-Algorithm
filters	I-Algorithm
at	O
10.7MHz	O
.	O
</s>
<s>
The	O
design	O
concept	O
for	O
utilizing	O
quartz	B-General_Concept
crystals	O
as	O
a	O
filtering	O
component	O
was	O
first	O
established	O
by	O
Walter	O
Cady	O
in	O
1922	O
,	O
but	O
it	O
was	O
largely	O
Warren	O
P	O
.	O
Mason	O
's	O
work	O
in	O
the	O
late	O
1920s	O
and	O
early	O
1930s	O
that	O
devised	O
methods	O
for	O
incorporating	O
crystals	O
into	O
LC	O
lattice	O
filter	O
networks	O
which	O
set	O
the	O
groundwork	O
for	O
much	O
of	O
the	O
progress	O
in	O
telephone	O
communications	O
.	O
</s>
<s>
Crystal	B-Algorithm
filter	I-Algorithm
designs	O
from	O
the	O
1960s	O
allowed	O
for	O
true	O
Chebyshev	O
,	O
Butterworth	O
,	O
and	O
other	O
typical	O
filter	O
characteristics	O
.	O
</s>
<s>
Crystal	B-Algorithm
filter	I-Algorithm
design	O
continued	O
to	O
improve	O
in	O
the	O
1970s	O
and	O
1980s	O
with	O
the	O
development	O
of	O
multi-pole	O
monolithic	O
filters	O
,	O
widely	O
used	O
today	O
to	O
provide	O
IF	O
selectivity	O
in	O
communication	O
receivers	O
.	O
</s>
<s>
Crystal	B-Algorithm
filters	I-Algorithm
can	O
be	O
found	O
today	O
in	O
radio	O
communications	O
,	O
telecommunications	O
,	O
signal	O
generation	O
,	O
and	O
GPS	O
devices	O
.	O
</s>
