User`s guide

Table Of Contents
122 Agilent E5505A User’s Guide
5
Absolute Measurement Fundamentals
Inserting a Device
An attenuator
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 DUT 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 test
set’s phase detector input port. The signal level required for the measurement
depends on the noise floor level needed to measure the DUT.
Figure 79 shows the relationship between the signal level at the R port and the
measurement noise floor.
Figure 79 Measurement noise floor relative to R-Port signal level