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Agilent E5505A User’s Guide
9
FM Discriminator Fundamentals
The Frequency Discriminator Method
Unlike the phase detector method, the frequency discriminator method does
not require a second reference source phase locked to the source under test.
See
.
This makes the frequency discriminator method extremely useful for
measuring sources that are difficult to phase lock, including sources that are
microphonic or drift quickly. It can also be used to measure sources with
high-level, low-rate phase noise, or high close-in spurious sidebands,
conditions with can pose serious problems for the phase detector method. A
wide-band delay line frequency discriminator is easy to implement using the
E5505A Phase Noise Measurement System and common coaxial cable.
Basic theory
The delay line implementation of the frequency discriminator (
converts short-term frequency fluctuations of a source into voltage
fluctuations that can be measured by a baseband analyzer. The conversion is a
two part process, first converting the frequency fluctuations into phase
fluctuations, and then converting the phase fluctuations to voltage
fluctuations.
The frequency fluctuation to phase fluctuation transformation (
) takes
place in the delay line. The nominal frequency arrives at the double-balanced
mixer at a particular phase. As the frequency changes slightly, the phase shift
incurred in the fixed delay time will change proportionally. The delay line
converts the frequency change at the line input to a phase change a the line
output when compared to the undelayed signal arriving at the mixer in the
second path.
Figure 178
Basic delay line/mixer frequency discriminator method
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Страница 24: ...24 Agilent E5505A User s Guide ...
Страница 46: ...46 Agilent E5505A User s Guide 2 Introduction and Measurement ...
Страница 128: ...128 Agilent E5505A User s Guide 5 Absolute Measurement Fundamentals ...
Страница 226: ...226 Agilent E5505A User s Guide 7 Residual Measurement Fundamentals ...
Страница 322: ...322 Agilent E5505A User s Guide 13 Baseband Noise Measurement Examples ...
Страница 340: ...340 Agilent E5505A User s Guide 14 Evaluating Your Measurement Results ...
Страница 358: ...358 Agilent E5505A User s Guide 15 Advanced Software Features ...
Страница 386: ...386 Agilent E5505A User s Guide 16 Reference Graphs and Tables ...
Страница 392: ...392 Agilent E5505A User s Guide 17 System Specifications ...
Страница 404: ...404 Agilent E5505A User s Guide 18 System Interconnections ...
Страница 452: ...452 Agilent E5505A User s Guide 20 PC Digitizer Performance Verification ...
Страница 466: ...466 Agilent E5505A User s Guide 21 Preventive Maintenance ...