Agilent Technologies HP 83711A - Page 132

EXT
METER
The
4
EXT
METER
5
key
enables
external
power
meter
leveling.
External
power
meter
leveling
is
a
method
of
automatic
level
control
(ALC)
of
the
output
signal
using
an
external
power
meter
and
power
sensor
.
When
the
4
EXT
METER
5
key
is
pressed,
you
are
prompted
to
put
the
power
meter
in
the
range
hold
mode
and
then
enter
the
power
meter reading
into
the
synthesizer
.
After
the
range
hold
power
meter
value
is
entered,
the
MTR
annunciator
will
be
lit.
If
the
procedure
,
\T
o
Use
External
P
ower
Meter
Leveling"
in
Chapter
3
has
been
followed
correctly
,
the
RF
output
will
be
externally
leveled
via
the
power
meter
feedback
loop
.
N
O
T
E
The
range
hold
power
meter
reading
is
the
power
level that
is
used
b
y
the
synthesizer
to
calibrate
the
recorder
output voltage
of
the
power
meter
versus
the
synthesizer
output
power
.
External
P
ower
Meter
Leveling
The
purpose
of
a
leveling
circuit
is
to
provide
constant
power
,
independent of
the
load,
and
minimize
power
variations
versus
frequency
.
External power meter leveling is used in applications where it is desired to
level the power at some point outside the synthesizer with an external power
meter. 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
6-20