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11
FM Discriminator Measurement Examples
Introduction
Introduction
11-2
E5500 Phase Noise Measurement System Version A.02.00
These two measurement examples demostrates the FM Discriminator
measurement technique for measuring the phase noise of a signal
source using two different calibration methods.
These measurement techniques work well for measuring
free-running oscillators that drift over a range that exceeds the
tuning range limits of the phase-locked-loop measurement technique.
The Discriminator measurement is also useful for measuring sources
when a VCO reference source is not available to provide adequate
drift tracking.
The setup for a discriminator measurement uses a delay line to
convert frequency fluctuations to phase fluctuations and a phase
shifter to set quadrature at the phase detector.
In the Discriminator measurement, the source is placed ahead of the
power splitter. One output of the splitter feeds a delay line with
enough delay to decorated the source noise. The delay line generates
a phase shift proportional to the frequency. The phase shift is
measured in the phase detector by comparing the delay output with
the other output from the splitter. The output of the phase detector is
a voltage proportional to the frequency fluctuations of the source.
For more information about FM Discrimination basics, refer to
Chapter
10, "FM Discriminator Fundamentals".
Document Part No. E5500-90024 Ed. 1.0
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