Agilent Technologies HP 83711A - EXT DIODE

EXT
DIODE
The
4
EXT
DIODE
5
key
enables
external
diode
leveling.
External
diode
leveling
is
a
method
of
automatic
level
control
(ALC)
of
the
output
signal
using
an
external
diode
detector
.
When
the
4
EXT
DIODE
5
key
is
pressed,
the
DIODE
annunciator
will
be
lit.
If
the
procedure
,
\T
o
Use
External
Diode
Detector
Leveling"
in
Chapter 3
has
been
followed
correctly
,
the
synthesizer
RF
output
will
be
externally
leveled
via
the
diode
detector
feedback
loop
.
External
Diode
Detector
Leveling
The
purpose
of
a
leveling
circuit
is
to
provide constant
power
,
independent
of
the
load,
and
minimize
power
variations
versus
frequency
.
External
diode
detector
leveling
is
used
in
applications
where
it
is desired
to
level
the
power
at
some
point
outside
the
synthesizer
with an
external
diode
detector
.
When
frequency
dependent
losses
are
involved,
the
RF output
power
at
the end
of the
signal
path
will
not
have
a
constant
amplitude
over
the synthesizer
frequency range
.F
or example
,
if
a
cable
is
used
at
the
output
of the
synthesizer that
has a
constant 0.5
dB/GHz
loss
,
5
dB
of
attenuation
at
the
output
of the
cable occurs
after a
10
GHz
frequency
increase
,
even
though
the
power
at the
input to
the cable
is
constant.
By
externally
leveling
power
at
the
output of
the cable
,the
synthesizer would
increase
power
at
the
input
of the
cable
to
produce
a
constant
power
level
at
the
output
of
the
cable
.
External
diode
detector
leveling
requires
that
external
equipment
be
connected to the synthesizer
, as shown in Figure 6-1
.
6-16