<s>
An	O
isolator	B-Algorithm
is	O
a	O
two-port	B-Algorithm
device	O
that	O
transmits	O
microwave	O
or	O
radio	O
frequency	O
power	O
in	O
one	O
direction	O
only	O
.	O
</s>
<s>
An	O
isolator	B-Algorithm
is	O
a	O
non-reciprocal	O
device	O
,	O
with	O
a	O
non-symmetric	O
scattering	O
matrix	O
.	O
</s>
<s>
To	O
achieve	O
non-reciprocity	O
,	O
an	O
isolator	B-Algorithm
must	O
necessarily	O
incorporate	O
a	O
non-reciprocal	O
material	O
.	O
</s>
<s>
The	O
ferrite	O
is	O
positioned	O
within	O
the	O
isolator	B-Algorithm
such	O
that	O
the	O
microwave	O
signal	O
presents	O
it	O
with	O
a	O
rotating	O
magnetic	O
field	O
,	O
with	O
the	O
rotation	O
axis	O
aligned	O
with	O
the	O
direction	O
of	O
the	O
static	O
bias	O
field	O
.	O
</s>
<s>
Most	O
common	O
types	O
of	O
ferrite-based	O
isolators	B-Algorithm
are	O
classified	O
into	O
four	O
categories	O
:	O
terminated	O
circulators	O
,	O
Faraday	O
rotation	O
isolators	B-Algorithm
,	O
field-displacement	O
isolators	B-Algorithm
,	O
and	O
resonance	O
isolators	B-Algorithm
.	O
</s>
<s>
For	O
a	O
given	O
bias	O
field	O
,	O
resonance	O
absorption	O
occurs	O
over	O
a	O
fairly	O
narrow	O
frequency	O
band	O
,	O
but	O
since	O
in	O
practice	O
the	O
bias	O
field	O
is	O
not	O
perfectly	O
uniform	O
throughout	O
the	O
ferrite	O
,	O
the	O
isolator	B-Algorithm
functions	O
over	O
a	O
somewhat	O
wider	O
band	O
.	O
</s>
<s>
This	O
type	O
is	O
superficially	O
very	O
similar	O
to	O
a	O
resonance	O
absorption	O
isolator	B-Algorithm
,	O
but	O
the	O
magnetic	O
biasing	O
differs	O
,	O
and	O
the	O
energy	O
from	O
the	O
backward	O
travelling	O
signal	O
is	O
absorbed	O
in	O
a	O
resistive	O
film	O
or	O
card	O
on	O
one	O
face	O
of	O
the	O
ferrite	O
block	O
rather	O
than	O
within	O
the	O
ferrite	O
itself	O
.	O
</s>
<s>
A	O
two-port	B-Algorithm
isolator	B-Algorithm
is	O
obtained	O
simply	O
by	O
terminating	O
one	O
of	O
the	O
three	O
ports	O
with	O
a	O
matched	O
load	O
,	O
which	O
absorbs	O
all	O
the	O
power	O
entering	O
it	O
.	O
</s>
<s>
The	O
bias	O
field	O
is	O
lower	O
than	O
that	O
needed	O
for	O
resonance	O
absorption	O
,	O
and	O
so	O
this	O
type	O
of	O
isolator	B-Algorithm
does	O
not	O
require	O
such	O
a	O
heavy	O
permanent	O
magnet	O
.	O
</s>
<s>
Because	O
the	O
power	O
is	O
absorbed	O
in	O
an	O
external	O
load	O
,	O
cooling	O
is	O
less	O
of	O
a	O
problem	O
than	O
with	O
a	O
resonance	O
absorption	O
isolator	B-Algorithm
.	O
</s>
<s>
A	O
last	O
physical	O
principle	O
useful	O
to	O
design	O
isolators	B-Algorithm
is	O
the	O
Faraday	O
rotation	O
.	O
</s>
<s>
This	O
rotation	O
may	O
be	O
used	O
to	O
create	O
microwave	O
devices	O
as	O
isolators	B-Algorithm
,	O
circulators	O
,	O
gyrators	O
,	O
etc	O
.	O
</s>
