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Phase noise
is often overlooked in a frequency reference but it is a
very important parameter.
By using
low phase noise references and distribution amplifiers,
an improvement to existing test equipment can be made.
Marconi 2024 Signal Generator - Internal Reference
Refer to
the picture below.
The
picture above
shows the phase noise of the authors own Marconi 2024
signal generator. The 2024 was set to 10 MHz and
its internal reference oscillator was used. This
Marconi 2024 has the optional high stability reference
installed. The Marconi 2024 was compared with a
CFS10B-03, our own ultra low noise 10 MHz reference.
The CFS10B-03 has phase noise of -112 dBc/Hz @ 1 Hz
offset with a -168 dBc/Hz noise floor. So, as this
reference, is much better than the Marconi 2024, it does
not influence the results. Thus, the above phase
noise plot is the true noise of the Marconi 2024.
The phase
noise is typical of this type of equipment. The
phase noise was -81 dBc/Hz at a 1 Hz offset with a -145
dBc/Hz noise floor.
Marconi 2024 Signal Generator - External Reference
The
Marconi 2024 was now set to use an external reference.
Another CFS10B-03 was used as the external reference.
The phase
noise was again measured in exactly the same way as
before.
See how
the phase noise at 1 Hz offset is 26 dB better and 10 dB
better at 10 Hz offset. This amazing improvement
is due to the Marconi 2024 now having an ultra low noise
reference. This phase noise will also improve the
Marconi 2024's Allan variance.
Other
Test Equipment
The same
theory as above applies to other types of test equipment
such as spectrum analyzers, tracking generators, or any
equipment that accepts an external 10 MHz. For
example the authors own HP8561B 6.5 GHz spectrum
analyzer was compared with an internal and external
reference. The signal response 10 Hz away from the
carrier again should a 10 dB improvement when the
external low phase noise reference was used..
Summary
Using an
ultra low phase noise frequency standard and
distribution amplifier system not only synchronizes all
of the equipment to a common accurate frequency
standard, but the actual test equipments' performance can
be improved using an ultra low phase noise external
reference.
Precision
Test systems manufacturers some of the industries lowest
phase noise frequency standards and distribution
amplifiers.
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