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Inserting a Device
An Attenuator
An Amplifier
Document Part No. E5500-90024Ed. 1.0
You may find that some of your measurement setups require an
in-line device such as an attenuator in one of the signal source paths.
(For example, you may find it necessary to insert an attenuator at the
output of a unit-under-test (UUT) to prevent it from being injection
locked to the reference source.) The primary consideration when
inserting an attenuator is that the signal source has sufficient output
amplitude to maintain the required signal level at the Agilent
70420A's phase detector input port. The signal level required for the
measurement depends on the noise floor level needed to measure the
UUT.
Figure 6-9
shows the relationship between the signal level at the R
port and the measurement noise floor.
Figure 6-9 Measurement Noise Floor Relative to R Port Signal Level.
If a source is not able to provide a sufficient output level, or if
additional isolation is needed at the output, it may be necessary to
insert a low phase-noise RF amplifier at the output of the source.
Note, however, that the noise of the inserted amplifier will also be
summed into the measured noise level along with the noise of the
source.
The Agilent 70427A Option K22 dual RF amplifier was designed
specifically for this purpose. This instrument is the preferred
solution for tests requiring an external amplifier.
E5500 Phase Noise Measurement System Version A.02.00
Absolute Measurement Fundamentals
Inserting a Device
6
6-19
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