280 Keysight NFA Series Noise Figure Analyzers Service Guide
L.O. Synthesizer/Reference Troubleshooting
A16 Reference Assembly Description
A16 Reference Assembly Description
Purpose
The A16 Reference Assembly provides the fundamental reference signals from
which all instrument local oscillator and synchronous timing signals are
derived The reference board also uses these same signals to generate CW and
modulated RF calibration signals and a 10 MHz time base signal for the
instrument
The Reference assembly must be replaced as a single assembly, although it is
constructed of two boards, the A16 Reference Main board and A16A1
Reference Daughter board. These boards are listed individually in the Show
Hardware screen, allowing identification of the individual board part numbers
comprising the complete assembly.
The reference signals and local oscillators can be phase locked to a timebase
in one of two ways:
1. The internal 10 MHz reference located on the A16 Main Board.
2. An externally provided reference such as a house standard or the reference
from another instrument or a base transceiver system. The external
reference can be any RF signal in the range of 1 MHz to 50 MHz, -5 dBm to
+10 dBm.
If an external reference signal is within 200 Hz of the specified external
reference frequency and Freq Ref In is set to Sense, the analyzer will
automatically switch from SENSE:INT to SENSE:EXT.
The frequency accuracy of the analyzer is directly tied to the accuracy of the
frequency reference that is being used.
Diagnostic LEDs monitor the status of the various PLLs on the A16 Reference
Assembly.
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