Performance Evaluation
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CG635 Synthesized Clock Generator
Performance Evaluation
Overview
The performance of a CG635 may be evaluated by running a series of tests designed to
measure the accuracy of its inputs and outputs and comparing the results with their
associated specifications. While the performance tests presented here are not as extensive
as the tests performed at the factory, one can nevertheless have confidence that a unit that
passes these tests is functioning properly and within specification.
The performance tests can be divided into three broad categories: output driver tests,
frequency synthesis tests, and timebase calibration tests. The output driver tests are
designed to test the integrity and accuracy of the front panel outputs by measuring the
accuracy with which its levels are generated and the speed with which it transitions
between levels. The frequency synthesis tests are designed to measure the stability of the
frequency synthesis by measuring the phase noise and jitter at specified frequencies.
Overall functionality is verified by measuring the frequency generation at various points
in the spectrum from DC to 2.05 GHz. Lastly, the timebase calibration tests evaluate the
accuracy and stability of the installed timebase.
Equipment Required
In addition to the CG635 under test, the following equipment will be required to carry out
the performance tests:
•
Agilent 34401A digital multimeter
•
HP 54120A digitizing oscilloscope with HP 54121A four channel input module
•
CG646 +7 dBm RF receiver module
•
FS725 rubidium frequency standard
•
HP 89440A spectrum analyzer
•
SR620/SR625 time interval counter (SR625 needed to test to 2 GHz)
Equivalent equipment may be substituted as desired as long as they have similar or
superior specifications. Standard SMA and BNC cables will be required to connect the
test equipment to the CG635. Additionally accessories required include, 50
terminators
for the CG635’s high frequency outputs and 20 dB DC to 18 GHz SMA attenuators for
the HP 54121A inputs.
CG635 Self Test
The CG635 includes a self test that checks the functional operation of several internal
components. If any of the tests fail, the CG635 will briefly display “Failed” after the test.
The tests are described in Table 16. In most cases the unit will have to be repaired by a
qualified technician if the unit fails one of these tests.