<s>
A	O
backward	B-Algorithm
wave	I-Algorithm
oscillator	I-Algorithm
(	O
BWO	O
)	O
,	O
also	O
called	O
carcinotron	B-Algorithm
or	O
backward	B-Algorithm
wave	I-Algorithm
tube	I-Algorithm
,	O
is	O
a	O
vacuum	O
tube	O
that	O
is	O
used	O
to	O
generate	O
microwaves	O
up	O
to	O
the	O
terahertz	B-Architecture
range	O
.	O
</s>
<s>
It	O
sustains	O
the	O
oscillations	B-Algorithm
by	O
propagating	O
a	O
traveling	O
wave	O
backwards	O
against	O
the	O
beam	O
.	O
</s>
<s>
Carcinotrons	B-Algorithm
are	O
used	O
as	O
powerful	O
and	O
stable	O
microwave	O
sources	O
.	O
</s>
<s>
Due	O
to	O
the	O
good	O
quality	O
wavefront	O
they	O
produce	O
(	O
see	O
below	O
)	O
,	O
they	O
find	O
use	O
as	O
illuminators	O
in	O
terahertz	B-Architecture
imaging	O
.	O
</s>
<s>
The	O
M-type	O
BWO	O
is	O
a	O
voltage-controlled	O
non-resonant	O
extrapolation	O
of	O
magnetron	B-Device
interaction	O
.	O
</s>
<s>
They	O
can	O
be	O
swept	O
through	O
the	O
band	O
fast	O
enough	O
to	O
be	O
appearing	O
to	O
radiate	O
over	O
all	O
the	O
band	O
at	O
once	O
,	O
which	O
makes	O
them	O
suitable	O
for	O
effective	O
radar	B-Application
jamming	O
,	O
quickly	O
tuning	O
into	O
the	O
radar	B-Application
frequency	O
.	O
</s>
<s>
Carcinotrons	B-Algorithm
allowed	O
airborne	O
radar	B-Application
jammers	O
to	O
be	O
highly	O
effective	O
.	O
</s>
<s>
However	O
,	O
frequency-agile	B-Algorithm
radars	B-Application
can	O
hop	O
frequencies	O
fast	O
enough	O
to	O
force	O
the	O
jammer	O
to	O
use	O
barrage	O
jamming	O
,	O
diluting	O
its	O
output	O
power	O
over	O
a	O
wide	O
band	O
and	O
significantly	O
impairing	O
its	O
efficiency	O
.	O
</s>
<s>
Carcinotrons	B-Algorithm
are	O
used	O
in	O
research	O
,	O
civilian	O
and	O
military	O
applications	O
.	O
</s>
<s>
For	O
example	O
,	O
the	O
Czechoslovak	O
Kopac	O
passive	O
sensor	O
and	O
Ramona	O
passive	O
sensor	O
air	O
defense	O
detection	O
systems	O
employed	O
carcinotrons	B-Algorithm
in	O
their	O
receiver	O
systems	O
.	O
</s>
<s>
In	O
systems	O
like	O
the	O
magnetron	B-Device
or	O
klystron	O
,	O
this	O
is	O
accomplished	O
with	O
another	O
resonant	O
cavity	O
.	O
</s>
<s>
The	O
"	O
problem	O
"	O
with	O
traditional	O
designs	O
is	O
that	O
they	O
have	O
relatively	O
narrow	O
bandwidths	B-Algorithm
;	O
designs	O
based	O
on	O
resonators	O
will	O
work	O
with	O
signals	O
within	O
10%	O
or	O
20%	O
of	O
their	O
design	O
,	O
as	O
this	O
is	O
physically	O
built	O
into	O
the	O
resonator	O
design	O
,	O
while	O
the	O
helix	O
designs	O
have	O
a	O
much	O
wider	O
bandwidth	B-Algorithm
,	O
perhaps	O
100%	O
on	O
either	O
side	O
of	O
the	O
design	O
peak	O
.	O
</s>
<s>
The	O
complex	O
serpentine	O
waveguide	O
places	O
strict	O
limits	O
on	O
the	O
bandwidth	B-Algorithm
of	O
the	O
input	O
signal	O
,	O
such	O
that	O
a	O
standing	O
wave	O
is	O
formed	O
within	O
the	O
guide	O
.	O
</s>
<s>
The	O
device	O
was	O
originally	O
given	O
the	O
name	O
"	O
carcinotron	B-Algorithm
"	O
because	O
it	O
was	O
like	O
cancer	O
to	O
existing	O
radar	B-Application
systems	I-Application
.	O
</s>
<s>
By	O
simply	O
changing	O
the	O
supply	O
voltage	O
,	O
the	O
device	O
could	O
produce	O
any	O
required	O
frequency	O
across	O
a	O
band	O
that	O
was	O
much	O
larger	O
than	O
any	O
existing	O
microwave	O
amplifier	O
could	O
match	O
-	O
the	O
cavity	B-Architecture
magnetron	I-Architecture
worked	O
at	O
a	O
single	O
frequency	O
defined	O
by	O
the	O
physical	O
dimensions	O
of	O
their	O
resonators	O
,	O
and	O
while	O
the	O
klystron	O
amplified	O
an	O
external	O
signal	O
,	O
it	O
only	O
did	O
so	O
efficiently	O
within	O
a	O
small	O
range	O
of	O
frequencies	O
.	O
</s>
<s>
Previously	O
,	O
jamming	O
a	O
radar	B-Application
was	O
a	O
complex	O
and	O
time-consuming	O
operation	O
.	O
</s>
<s>
When	O
the	O
radar	B-Application
station	I-Application
realized	O
what	O
was	O
happening	O
,	O
they	O
would	O
change	O
their	O
frequencies	O
and	O
the	O
process	O
would	O
begin	O
again	O
.	O
</s>
<s>
In	O
contrast	O
,	O
the	O
carcinotron	B-Algorithm
could	O
sweep	O
through	O
all	O
the	O
possible	O
frequencies	O
so	O
rapidly	O
that	O
it	O
appeared	O
to	O
be	O
a	O
constant	O
signal	O
on	O
all	O
of	O
the	O
frequencies	O
at	O
once	O
.	O
</s>
<s>
Typical	O
designs	O
could	O
generate	O
hundreds	O
or	O
low	O
thousands	O
of	O
watts	O
,	O
so	O
at	O
any	O
one	O
frequency	O
,	O
there	O
might	O
be	O
a	O
few	O
watts	O
of	O
power	O
that	O
is	O
received	O
by	O
the	O
radar	B-Application
station	I-Application
.	O
</s>
<s>
However	O
,	O
at	O
long	O
range	O
the	O
amount	O
of	O
energy	O
from	O
the	O
original	O
radar	B-Application
broadcast	O
that	O
reaches	O
the	O
aircraft	O
is	O
only	O
a	O
few	O
watts	O
at	O
most	O
,	O
so	O
the	O
carcinotron	B-Algorithm
can	O
overpower	O
them	O
.	O
</s>
<s>
The	O
system	O
was	O
so	O
powerful	O
that	O
it	O
was	O
found	O
that	O
a	O
carcinotron	B-Algorithm
operating	O
on	O
an	O
aircraft	O
would	O
begin	O
to	O
be	O
effective	O
even	O
before	O
it	O
rose	O
above	O
the	O
radar	B-Algorithm
horizon	I-Algorithm
.	O
</s>
<s>
As	O
it	O
swept	O
through	O
the	O
frequencies	O
it	O
would	O
broadcast	O
on	O
the	O
radar	B-Application
's	O
operating	O
frequency	O
at	O
what	O
were	O
effectively	O
random	O
times	O
,	O
filling	O
the	O
display	O
with	O
random	O
dots	O
any	O
time	O
the	O
antenna	O
was	O
pointed	O
near	O
it	O
,	O
perhaps	O
3	O
degrees	O
on	O
either	O
side	O
of	O
the	O
target	O
.	O
</s>
<s>
At	O
close	O
range	O
,	O
on	O
the	O
order	O
of	O
,	O
the	O
entire	O
radar	B-Algorithm
display	I-Algorithm
would	O
be	O
completely	O
filled	O
with	O
noise	O
,	O
rendering	O
it	O
useless	O
.	O
</s>
<s>
The	O
concept	O
was	O
so	O
powerful	O
as	O
a	O
jammer	O
that	O
there	O
were	O
serious	O
concerns	O
that	O
ground-based	O
radars	B-Application
were	O
obsolete	O
.	O
</s>
<s>
Airborne	O
radars	B-Application
had	O
the	O
advantage	O
that	O
they	O
could	O
approach	O
the	O
aircraft	O
carrying	O
the	O
jammer	O
,	O
and	O
,	O
eventually	O
,	O
the	O
huge	O
output	O
from	O
their	O
transmitter	O
would	O
"	O
burn	O
through	O
"	O
the	O
jamming	O
.	O
</s>
<s>
However	O
,	O
interceptors	O
of	O
the	O
era	O
relied	O
on	O
ground	O
direction	O
to	O
get	O
into	O
range	O
,	O
using	O
ground-based	O
radars	B-Application
.	O
</s>
<s>
For	O
ground	O
radars	B-Application
,	O
the	O
threat	O
was	O
eventually	O
solved	O
in	O
two	O
ways	O
.	O
</s>
<s>
The	O
first	O
was	O
that	O
radars	B-Application
were	O
upgraded	O
to	O
operate	O
on	O
many	O
different	O
frequencies	O
and	O
switch	O
among	O
them	O
randomly	O
from	O
pulse	O
to	O
pulse	O
,	O
a	O
concept	O
now	O
known	O
as	O
frequency	B-Algorithm
agility	I-Algorithm
.	O
</s>
<s>
The	O
carcinotron	B-Algorithm
could	O
still	O
sweep	O
through	O
the	O
entire	O
band	O
,	O
but	O
then	O
it	O
would	O
be	O
broadcasting	O
on	O
the	O
same	O
frequency	O
as	O
the	O
radar	B-Application
only	O
at	O
random	O
times	O
,	O
reducing	O
its	O
effectiveness	O
.	O
</s>
<s>
The	O
other	O
solution	O
was	O
to	O
add	O
passive	O
receivers	O
that	O
triangulated	O
on	O
the	O
carcinotron	B-Algorithm
broadcasts	O
,	O
allowing	O
the	O
ground	O
stations	O
to	O
produce	O
accurate	O
tracking	O
information	O
on	O
the	O
location	O
of	O
the	O
jammer	O
and	O
allowing	O
them	O
to	O
be	O
attacked	O
.	O
</s>
<s>
The	O
M-type	O
carcinotron	B-Algorithm
,	O
or	O
M-type	O
backward	B-Algorithm
wave	I-Algorithm
oscillator	I-Algorithm
,	O
uses	O
crossed	O
static	O
electric	O
field	O
E	O
and	O
magnetic	O
field	O
B	O
,	O
similar	O
to	O
the	O
magnetron	B-Device
,	O
for	O
focussing	O
an	O
electron	O
sheet	O
beam	O
drifting	O
perpendicularly	O
to	O
E	O
and	O
B	O
,	O
along	O
a	O
slow-wave	O
circuit	O
,	O
with	O
a	O
velocity	O
E/B	O
.	O
</s>
<s>
The	O
O-type	O
carcinotron	B-Algorithm
,	O
or	O
O-type	O
backward	B-Algorithm
wave	I-Algorithm
oscillator	I-Algorithm
,	O
uses	O
an	O
electron	O
beam	O
longitudinally	O
focused	O
by	O
a	O
magnetic	O
field	O
,	O
and	O
a	O
slow-wave	O
circuit	O
interacting	O
with	O
the	O
beam	O
.	O
</s>
<s>
The	O
oscillation	B-Algorithm
starts	O
at	O
a	O
frequency	O
where	O
the	O
wave	O
propagating	O
on	O
the	O
circuit	O
is	O
synchronous	O
with	O
the	O
slow	O
space	O
charge	O
wave	O
of	O
the	O
beam	O
.	O
</s>
<s>
The	O
oscillation	B-Algorithm
frequency	O
is	O
also	O
sensitive	O
to	O
the	O
beam	O
current	O
(	O
called	O
"	O
frequency	O
pushing	O
"	O
)	O
.	O
</s>
