User`s guide

Residual Measurement Fundamentals 7
Agilent E5505A User’s Guide 207
Frequency translation devices
If the DUT is a frequency translating device (such as a divider, multiplier, or
mixer), then one DUT must be put in each path. The result is the sum of the
noise from each DUT. In other words, each DUT is at least as quiet as the
measured result.
If the DUTs are identical, a possible (but not recommended) assumption is that
the noise of each DUT is half the measured result, or 3 dB less. All that really
can be concluded is that the noise level of one of the DUTs is at least 3 dB
lower than the measured result at any particular offset frequency.
If a more precise determination is required at any particular offset frequency,
a third DUT must also be measured against the other two DUTs. The data from
each of the three measurements can then be processed by the phase noise
software to give the noise of each of the individual DUTs. See Figure 146.
Figure 146 Measurement setup for two similar DUTs
Phase
detector
Power
splitter
Source
Base band
analysis
E5505a_meas_setup_two
27 Feb 04 rev 1
Device
under
test
Device
under
test