HA7062D Manual Rev 1.01
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Page 60 of 105
11.0 MEASUREMENT EXAMPLES
11.1 ADDITIVE MEASUREMENTS (<6GHz)
Additive measurement block diagrams and examples are shown in the next two sub-sections
demonstrating these measurements using both mechanical and HX5100 phase shifters. The signal
used to drive the measurement is split into three paths; one passes through the DUT and the other
two are fed through phase shifters to the instrument LO inputs. The phase shifters are used to align
quadrature (90° offset) between the signals fed into the DUT and LO ports. The following points are
critical to performing the best additive measurement possible.
Two measurements should be made. The first measurement is a noise floor measurement and
is taken without the DUT in the system, cabling the DUT path from the output of the divider
directly into the instrument rather than through the DUT. The second measurement is the added
noise due to the DUT in the system.
The LO inputs optimal drive range is +7 to +13 dBm. The minimum acceptable input is +3dBm
and +13dBm is the maximum for proper phase detector operation. +7dBm to +13dBm ensures
the greatest measurement sensitivity. The DUT input may be -5dBm to +20dBm.
The time delay in the LO paths and DUT paths should be matched as closely as possible. If
there is too great of a difference in time delay the source will not cancel as effectively.
Ineffective source cancellation results in measuring the phase noise of the source as opposed
to the true noise of the DUT.
A fixed frequency source is generally recommended. Source noise will cancel out, however a
higher performing source (lower phase noise) is recommended.