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Downconverter Operation
Phase Noise Measurement <26.5 GHz System Control
Step 1 - Decide which instrument to tune
There are three choices for phase locking: by using either the DUT; the
reference source; or for frequencies
be turned.
Tuning the HP 8662A/3A
If the DUT is referenced to an oven stabilized oscillator, the HP 8662A/3A
can be tuned. Connect the tune line to the EFC input. The limitation is that
the HP 8662A/3A's EFC can only track a drift of 10
frequency from the downconverter.
The HP 8662A/3A can also be tuned by setting the modulation to
DC FM. Refer to the HP 3048A manual for more information on tuning the
HP 8662A/3A.
Tuning the HP 70427A
If the DUT is a room-temperature oscillator, the downconverter's LO should
be tuned. The downconverter's tuning sensitivity can be selected so that it's
tuning range will be greater than the expected drift of the DUT.
The choices are:
•
1.0 ppm/V (600 MHz PLL bandwidth must be greater than
the HP 3048A PLL bandwidth)
•
20 ppm/V
Noise performance depends on tuning sensitivity so it may be necessary to
trade off noise performance for tuning range. Refer to a specification table in
chapter 9 for noise performance for each tuning sensitivity.
Tuning the DUT:
Refer to the Signal Source Applications chapter of the HP 3048A manual
for information on tuning the DUT.
Step 2 - Define the measurement
Follow the instructions in the HP 3048A manual together with the
information below:
1. System Configuration
•
Enter the downconverter in the system configuration table. Refer to
chapter 1 in this manual for information on determining and setting the
HP 70427A's HP-IB address.
2. Specify Measurement Type and Frequency Range
•
Measurement type: Phase Noise Using a Phase-Lock-Loop
3-22 HP 70427A/HP 70428A User's Guide
≥
1.5.GHz the downconverter's LO can
-8
of the output
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