<s>
A	O
Gunn	B-Algorithm
diode	I-Algorithm
,	O
also	O
known	O
as	O
a	O
transferred	B-Algorithm
electron	I-Algorithm
device	I-Algorithm
(	O
TED	O
)	O
,	O
is	O
a	O
form	O
of	O
diode	O
,	O
a	O
two-terminal	O
semiconductor	O
electronic	O
component	O
,	O
with	O
negative	O
resistance	O
,	O
used	O
in	O
high-frequency	O
electronics	O
.	O
</s>
<s>
It	O
is	O
based	O
on	O
the	O
"	O
Gunn	B-Algorithm
effect	I-Algorithm
"	O
discovered	O
in	O
1962	O
by	O
physicist	O
J	O
.	O
</s>
<s>
Its	O
largest	O
use	O
is	O
in	O
electronic	O
oscillators	O
to	O
generate	O
microwaves	O
,	O
in	O
applications	O
such	O
as	O
radar	O
speed	O
guns	O
,	O
microwave	B-Application
relay	I-Application
data	O
link	O
transmitters	O
,	O
and	O
automatic	O
door	O
openers	O
.	O
</s>
<s>
Its	O
internal	O
construction	O
is	O
unlike	O
other	O
diodes	O
in	O
that	O
it	O
consists	O
only	O
of	O
N-doped	B-Algorithm
semiconductor	O
material	O
,	O
whereas	O
most	O
diodes	O
consist	O
of	O
both	O
P	O
and	O
N-doped	B-Algorithm
regions	O
.	O
</s>
<s>
It	O
therefore	O
conducts	O
in	O
both	O
directions	O
and	O
cannot	O
rectify	B-Algorithm
alternating	O
current	O
like	O
other	O
diodes	O
,	O
which	O
is	O
why	O
some	O
sources	O
do	O
not	O
use	O
the	O
term	O
diode	O
but	O
prefer	O
TED	O
.	O
</s>
<s>
In	O
the	O
Gunn	B-Algorithm
diode	I-Algorithm
,	O
three	O
regions	O
exist	O
:	O
two	O
of	O
those	O
are	O
heavily	O
N-doped	B-Algorithm
on	O
each	O
terminal	O
,	O
with	O
a	O
thin	O
layer	O
of	O
lightly	O
n-doped	B-Algorithm
material	O
between	O
.	O
</s>
<s>
This	O
means	O
a	O
Gunn	B-Algorithm
diode	I-Algorithm
has	O
a	O
region	O
of	O
negative	O
differential	O
resistance	O
in	O
its	O
current	O
–	O
voltage	O
characteristic	O
curve	O
,	O
in	O
which	O
an	O
increase	O
of	O
applied	O
voltage	O
,	O
causes	O
a	O
decrease	O
in	O
current	O
.	O
</s>
<s>
In	O
practical	O
oscillators	O
,	O
an	O
electronic	O
resonator	O
is	O
usually	O
added	O
to	O
control	O
frequency	O
,	O
in	O
the	O
form	O
of	O
a	O
waveguide	O
,	O
microwave	B-Algorithm
cavity	I-Algorithm
or	O
YIG	B-Algorithm
sphere	I-Algorithm
.	O
</s>
<s>
The	O
diode	O
is	O
usually	O
mounted	O
inside	O
the	O
cavity	B-Algorithm
.	O
</s>
<s>
The	O
frequency	O
can	O
be	O
tuned	O
mechanically	O
,	O
by	O
adjusting	O
the	O
size	O
of	O
the	O
cavity	B-Algorithm
,	O
or	O
in	O
case	O
of	O
YIG	B-Algorithm
spheres	I-Algorithm
by	O
changing	O
the	O
magnetic	O
field	O
.	O
</s>
<s>
Gunn	B-Algorithm
diodes	I-Algorithm
are	O
used	O
to	O
build	O
oscillators	O
in	O
the	O
10	B-Algorithm
GHz	I-Algorithm
to	O
THz	B-Architecture
frequency	O
range	O
.	O
</s>
<s>
Gallium	O
arsenide	O
Gunn	B-Algorithm
diodes	I-Algorithm
are	O
made	O
for	O
frequencies	O
up	O
to	O
200GHz	O
,	O
gallium	O
nitride	O
materials	O
can	O
reach	O
up	O
to	O
3	O
terahertz	O
.	O
</s>
<s>
The	O
Gunn	B-Algorithm
diode	I-Algorithm
is	O
based	O
on	O
the	O
Gunn	B-Algorithm
effect	I-Algorithm
,	O
and	O
both	O
are	O
named	O
for	O
physicist	O
J	O
.	O
</s>
<s>
The	O
Gunn	B-Algorithm
effect	I-Algorithm
,	O
and	O
its	O
relation	O
to	O
the	O
Watkins	O
–	O
Ridley	O
–	O
Hilsum	O
effect	O
entered	O
electronics	O
literature	O
in	O
the	O
early	O
1970s	O
,	O
e.g.	O
</s>
<s>
in	O
books	O
on	O
transferred	B-Algorithm
electron	I-Algorithm
devices	I-Algorithm
and	O
,	O
more	O
recently	O
on	O
nonlinear	O
wave	O
methods	O
for	O
charge	O
transport	O
.	O
</s>
<s>
The	O
laboratory	O
methods	O
that	O
are	O
used	O
to	O
select	O
materials	O
for	O
the	O
manufacture	O
of	O
Gunn	B-Algorithm
diodes	I-Algorithm
include	O
angle-resolved	O
photoemission	O
spectroscopy	O
.	O
</s>
<s>
Because	O
of	O
their	O
high	O
frequency	O
capability	O
,	O
Gunn	B-Algorithm
diodes	I-Algorithm
are	O
mainly	O
used	O
at	O
microwave	O
frequencies	O
and	O
above	O
.	O
</s>
<s>
A	O
bias	B-Algorithm
tee	I-Algorithm
is	O
needed	O
to	O
isolate	O
the	O
bias	O
current	O
from	O
the	O
high	O
frequency	O
oscillations	O
.	O
</s>
<s>
Gunn	B-Algorithm
diode	I-Algorithm
oscillators	O
are	O
used	O
to	O
generate	O
microwave	O
power	O
for	O
:	O
airborne	O
collision	O
avoidance	O
radar	O
,	O
anti-lock	O
brakes	O
,	O
sensors	O
for	O
monitoring	O
the	O
flow	O
of	O
traffic	O
,	O
car	B-Application
radar	I-Application
detectors	I-Application
,	O
pedestrian	O
safety	O
systems	O
,	O
"	O
distance	O
travelled	O
"	O
recorders	O
,	O
motion	O
detectors	O
,	O
"	O
slow-speed	O
"	O
sensors	O
(	O
to	O
detect	O
pedestrian	O
and	O
traffic	O
movement	O
up	O
to	O
85	O
km/h	O
(	O
50	O
mph	O
)	O
)	O
,	O
traffic	O
signal	O
controllers	O
,	O
automatic	O
door	O
openers	O
,	O
automatic	O
traffic	O
gates	O
,	O
process	O
control	O
equipment	O
to	O
monitor	O
throughput	O
,	O
burglar	O
alarms	O
and	O
equipment	O
to	O
detect	O
trespassers	O
,	O
sensors	O
to	O
avoid	O
derailment	O
of	O
trains	O
,	O
remote	O
vibration	O
detectors	O
,	O
rotational	O
speed	O
tachometers	O
,	O
moisture	O
content	O
monitors	O
.	O
</s>
<s>
By	O
virtue	O
of	O
their	O
low	O
voltage	O
operation	O
,	O
Gunn	B-Algorithm
diodes	I-Algorithm
can	O
serve	O
as	O
microwave	O
frequency	O
generators	O
for	O
very	O
low	O
powered	O
(	O
few-milliwatt	O
)	O
microwave	O
transceivers	O
called	O
Gunnplexers	B-Algorithm
.	O
</s>
<s>
They	O
were	O
first	O
used	O
by	O
British	O
radio	O
amateurs	O
in	O
the	O
late	O
1970s	O
,	O
and	O
many	O
Gunnplexer	B-Algorithm
designs	O
have	O
been	O
published	O
in	O
journals	O
.	O
</s>
<s>
A	O
low	O
voltage	O
(	O
less	O
than	O
12	O
volt	O
)	O
direct	O
current	O
power	O
supply	O
,	O
that	O
can	O
be	O
modulated	B-Application
appropriately	O
,	O
is	O
used	O
to	O
drive	O
the	O
diode	O
.	O
</s>
<s>
The	O
waveguide	O
is	O
blocked	O
at	O
one	O
end	O
to	O
form	O
a	O
resonant	O
cavity	B-Algorithm
and	O
the	O
other	O
end	O
usually	O
feeds	O
a	O
horn	O
antenna	O
.	O
</s>
<s>
Gunnplexers	B-Algorithm
are	O
most	O
commonly	O
used	O
in	O
the	O
10	B-Algorithm
GHz	I-Algorithm
and	O
24	B-Algorithm
GHz	I-Algorithm
ham	O
bands	O
and	O
sometimes	O
22	O
GHz	O
security	O
alarms	O
are	O
modified	O
as	O
the	O
diode(s )	O
can	O
be	O
put	O
in	O
a	O
slightly	O
detuned	O
cavity	B-Algorithm
with	O
layers	O
of	O
copper	O
or	O
aluminium	O
foil	O
on	O
opposite	O
edges	O
for	O
moving	O
to	O
the	O
licensed	O
amateur	O
band	O
.	O
</s>
<s>
The	O
mixer	O
diode	O
is	O
useful	O
for	O
lower	O
frequency	O
applications	O
even	O
if	O
the	O
Gunn	B-Algorithm
diode	I-Algorithm
is	O
weakened	O
from	O
use	O
,	O
and	O
some	O
amateur	O
radio	O
enthusiasts	O
have	O
used	O
them	O
in	O
conjunction	O
with	O
an	O
external	O
oscillator	O
or	O
n/2	O
wavelength	O
Gunn	B-Algorithm
diode	I-Algorithm
for	O
satellite	O
finding	O
and	O
other	O
applications	O
.	O
</s>
<s>
Gunn	B-Algorithm
oscillators	I-Algorithm
are	O
used	O
as	O
local	O
oscillators	O
for	O
millimeter-wave	O
and	O
submillimeter-wave	O
radio	O
astronomy	O
receivers	O
.	O
</s>
<s>
The	O
Gunn	B-Algorithm
diode	I-Algorithm
is	O
mounted	O
in	O
a	O
cavity	B-Algorithm
tuned	O
to	O
resonate	O
at	O
twice	O
the	O
fundamental	O
frequency	O
of	O
the	O
diode	O
.	O
</s>
<s>
The	O
cavity	B-Algorithm
length	O
is	O
changed	O
by	O
a	O
micrometer	O
adjustment	O
.	O
</s>
<s>
Gunn	B-Algorithm
oscillators	I-Algorithm
capable	O
of	O
generating	O
over	O
50	O
mW	O
over	O
a	O
50%	O
tuning	O
range	O
(	O
one	O
waveguide	O
band	O
)	O
are	O
available	O
.	O
</s>
<s>
The	O
Gunn	B-Algorithm
oscillator	I-Algorithm
frequency	O
is	O
multiplied	O
by	O
a	O
diode	O
frequency	O
multiplier	O
for	O
submillimeter-wave	O
applications	O
.	O
</s>
