<s>
The	O
cheese	B-Algorithm
antenna	I-Algorithm
,	O
also	O
known	O
as	O
a	O
pillbox	O
antenna	O
,	O
is	O
a	O
type	O
of	O
microwave-frequency	O
parabolic	O
antenna	O
used	O
in	O
certain	O
types	O
of	O
radar	B-Application
.	O
</s>
<s>
When	O
the	O
antenna	O
is	O
wide	O
along	O
its	O
flat	O
axis	O
it	O
is	O
called	O
a	O
pillbox	O
antenna	O
and	O
when	O
narrow	O
a	O
cheese	B-Algorithm
antenna	I-Algorithm
.	O
</s>
<s>
Cheese	B-Algorithm
antennas	I-Algorithm
produce	O
a	O
beam	O
of	O
microwaves	O
that	O
is	O
narrow	O
in	O
the	O
antenna	O
's	O
curved	O
dimension	O
,	O
and	O
wide	O
in	O
the	O
flat	O
dimension	O
.	O
</s>
<s>
The	O
result	O
is	O
a	O
broad	O
fan-shaped	O
radiation	B-Device
pattern	I-Device
sometimes	O
called	O
a	O
beaver-tail	O
pattern	O
.	O
</s>
<s>
These	O
are	O
used	O
when	O
the	O
location	O
in	O
a	O
single	O
plane	O
is	O
desired	O
,	O
which	O
is	O
often	O
the	O
case	O
for	O
horizon-scanning	O
radars	B-Application
seen	O
on	O
ships	O
.	O
</s>
<s>
The	O
first	O
example	O
of	O
the	O
cheese	O
was	O
developed	O
for	O
the	O
Royal	O
Navy	O
's	O
Type	O
271	O
radar	B-Application
,	O
allowing	O
it	O
to	O
accurately	O
measure	O
the	O
bearing	O
to	O
a	O
target	O
while	O
having	O
a	O
wide	O
vertical	O
coverage	O
so	O
the	O
reflection	O
would	O
remain	O
in	O
the	O
beam	O
while	O
the	O
ship	O
pitched	O
up	O
and	O
down	O
in	O
the	O
waves	O
.	O
</s>
<s>
Similar	O
designs	O
may	O
also	O
be	O
found	O
in	O
height	B-Algorithm
finding	I-Algorithm
radars	I-Algorithm
,	O
with	O
the	O
antenna	O
turned	O
"	O
sideways	O
"	O
in	O
order	O
to	O
accurately	O
measure	O
the	O
elevation	O
angle	O
.	O
</s>
<s>
These	O
are	O
not	O
widespread	O
,	O
as	O
most	O
height	B-Algorithm
finders	I-Algorithm
used	O
a	O
modified	O
"	O
orange	O
peel	O
"	O
design	O
to	O
focus	O
in	O
azimuth	O
as	O
well	O
,	O
in	O
order	O
to	O
be	O
able	O
to	O
pick	O
out	O
a	O
single	O
aircraft	O
.	O
</s>
<s>
While	O
common	O
into	O
the	O
1960s	O
,	O
the	O
use	O
of	O
slot	B-Algorithm
antennas	I-Algorithm
and	O
phased	O
array	O
antennas	O
has	O
led	O
to	O
the	O
cheese	O
becoming	O
less	O
common	O
.	O
</s>
