<s>
In	O
the	O
field	O
of	O
antenna	O
design	O
the	O
term	O
radiation	B-Device
pattern	I-Device
(	O
or	O
antenna	B-Device
pattern	I-Device
or	O
far-field	B-Device
pattern	I-Device
)	O
refers	O
to	O
the	O
directional	O
(	O
angular	O
)	O
dependence	O
of	O
the	O
strength	O
of	O
the	O
radio	O
waves	O
from	O
the	O
antenna	O
or	O
other	O
source	O
.	O
</s>
<s>
Particularly	O
in	O
the	O
fields	O
of	O
fiber	B-Architecture
optics	I-Architecture
,	O
lasers	O
,	O
and	O
integrated	O
optics	O
,	O
the	O
term	O
radiation	B-Device
pattern	I-Device
may	O
also	O
be	O
used	O
as	O
a	O
synonym	O
for	O
the	O
near-field	B-Algorithm
pattern	O
or	O
Fresnel	O
pattern	O
.	O
</s>
<s>
This	O
refers	O
to	O
the	O
positional	O
dependence	O
of	O
the	O
electromagnetic	O
field	O
in	O
the	O
near	B-Algorithm
field	I-Algorithm
,	O
or	O
Fresnel	O
region	O
of	O
the	O
source	O
.	O
</s>
<s>
The	O
near-field	B-Algorithm
pattern	O
is	O
most	O
commonly	O
defined	O
over	O
a	O
plane	O
placed	O
in	O
front	O
of	O
the	O
source	O
,	O
or	O
over	O
a	O
cylindrical	O
or	O
spherical	O
surface	O
enclosing	O
it	O
.	O
</s>
<s>
The	O
far-field	B-Device
pattern	I-Device
of	O
an	O
antenna	O
may	O
be	O
determined	O
experimentally	O
at	O
an	O
antenna	O
range	O
,	O
or	O
alternatively	O
,	O
the	O
near-field	B-Algorithm
pattern	O
may	O
be	O
found	O
using	O
a	O
near-field	B-Algorithm
scanner	O
,	O
and	O
the	O
radiation	B-Device
pattern	I-Device
deduced	O
from	O
it	O
by	O
computation	O
.	O
</s>
<s>
The	O
far-field	B-Algorithm
radiation	I-Algorithm
pattern	I-Algorithm
can	O
also	O
be	O
calculated	O
from	O
the	O
antenna	O
shape	O
by	O
computer	O
programs	O
such	O
as	O
NEC	B-Protocol
.	O
</s>
<s>
Other	O
software	O
,	O
like	O
HFSS	B-Algorithm
can	O
also	O
compute	O
the	O
near	B-Algorithm
field	I-Algorithm
.	O
</s>
<s>
The	O
far	B-Algorithm
field	I-Algorithm
radiation	B-Device
pattern	I-Device
may	O
be	O
represented	O
graphically	O
as	O
a	O
plot	O
of	O
one	O
of	O
a	O
number	O
of	O
related	O
variables	O
,	O
including	O
;	O
the	O
field	O
strength	O
at	O
a	O
constant	O
(	O
large	O
)	O
radius	O
(	O
an	O
amplitude	O
pattern	O
or	O
field	B-Device
pattern	I-Device
)	O
,	O
the	O
power	O
per	O
unit	O
solid	O
angle	O
(	O
power	O
pattern	O
)	O
and	O
the	O
directive	O
gain	O
.	O
</s>
<s>
It	O
is	O
a	O
fundamental	O
property	O
of	O
antennas	O
that	O
the	O
receiving	O
pattern	O
(	O
sensitivity	O
as	O
a	O
function	O
of	O
direction	O
)	O
of	O
an	O
antenna	O
when	O
used	O
for	O
receiving	O
is	O
identical	O
to	O
the	O
far-field	B-Algorithm
radiation	I-Algorithm
pattern	I-Algorithm
of	O
the	O
antenna	O
when	O
used	O
for	O
transmitting	O
.	O
</s>
<s>
Therefore	O
,	O
in	O
discussions	O
of	O
radiation	B-Device
patterns	I-Device
the	O
antenna	O
can	O
be	O
viewed	O
as	O
either	O
transmitting	O
or	O
receiving	O
,	O
whichever	O
is	O
more	O
convenient	O
.	O
</s>
<s>
These	O
axially	O
symmetric	O
antennas	O
have	O
radiation	B-Device
patterns	I-Device
with	O
a	O
similar	O
symmetry	O
,	O
called	O
omnidirectional	O
patterns	O
;	O
they	O
radiate	O
equal	O
power	O
in	O
all	O
directions	O
perpendicular	O
to	O
the	O
antenna	O
,	O
with	O
the	O
power	O
varying	O
only	O
with	O
the	O
angle	O
to	O
the	O
axis	O
,	O
dropping	O
off	O
to	O
zero	O
on	O
the	O
antenna	O
's	O
axis	O
.	O
</s>
<s>
This	O
illustrates	O
the	O
general	O
principle	O
that	O
if	O
the	O
shape	O
of	O
an	O
antenna	O
is	O
symmetrical	O
,	O
its	O
radiation	B-Device
pattern	I-Device
will	O
have	O
the	O
same	O
symmetry	O
.	O
</s>
<s>
In	O
most	O
antennas	O
,	O
the	O
radiation	O
from	O
the	O
different	O
parts	O
of	O
the	O
antenna	O
interferes	O
at	O
some	O
angles	O
;	O
the	O
radiation	B-Device
pattern	I-Device
of	O
the	O
antenna	O
can	O
be	O
considered	O
an	O
interference	O
pattern	O
.	O
</s>
<s>
Instead	O
,	O
the	O
radiation	B-Device
pattern	I-Device
of	O
the	O
antenna	O
is	O
determined	O
by	O
a	O
single	O
simulation	O
,	O
and	O
the	O
receiving	O
pattern	O
inferred	O
by	O
reciprocity	O
.	O
</s>
