
AM Noise Measurements
The
AM
Noise measurement type
is
used
to
measure
the AM
Noise
on a
signal.
SOURCE CONTROL
FOR
fill NOISE MEASUREMENT
DUT SOURCE
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USER'S SRCE
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_RM DETECTOR
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USER'S DEV.
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Source Detect
Figure 2-4. Block Diagram of the AM Noise Measurement Configuration
AM Noise
can
contribute
to
phase noise when
a
phase noise measurement
is made. Phase detectors typically have
20 to 30 dB of AM
rejection.
Therefore,
the AM
Noise level should
not
exceed
the
level
of the
Phase
Noise
by
more than
20 dB to
insure that
the AM
Noise
is not
contributing
to
the
phase noise measurement results.
AM
Noise affects
the
results
of a
Phase Noise measurement using
an
FM Discriminator much more strongly.
An
FM
Discriminator implemented with
a
delay line
and
phase detector
becomes increasingly sensitive
to AM
Noise
at the
rate
of 20
dB/decade
as
the
offset frequency decreases below
^r.
Type/Range 2-7
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