Copyright: 1996 - 2024
BSEE - KB3UON
RF Cafe began life in 1996 as "RF Tools" in an AOL screen name web space totaling
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How to measure Phase Noise and Power Spectral Density - RF Cafe
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Below are the old forum threads, including responses to the original posts.
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Test & Measurement
Post subject: How to measure Phase Noise and Power Spectral
Unread postPosted: Thu Dec 30, 2004 5:04 am
measure Phase Noise (dBc/Hz) and Power Spectral Density (dBm/Hz) using
Unread postPosted: Thu Dec 30, 2004 2:07 pm
In most modern Spectrum Analyzers there is a built in feature that
measures the Phase Noise and plots it in logarithmic graph: Phase Noise
However, if you are using older Spectrum Analyzer,
you have to bring the carrier to the center by using MARKER>CF, then
placing the reference marker on the carrier and moving the delta marker
to the desired offset. The reading would be the Phase Noise (dBc/Hz).
You have to remember to add the attenuation of the RBW filter= 10 log
RBW to this reading. This filter further attenuates the Phase Noise.
I am not sure if you can get the Spectral Density VALUE with Spectrum
Analyzer. But you can measure the outpot power by Power Meter and make
the calculation based on the Phase Noise result.
Post subject: PSD measurement
Fri Dec 31, 2004 4:54 am
PSD is used when measuring continuous
broadband noise, and normalizes the power to an equivalent bandwidth
of 1 Hz, irrespective of the actual bandwidth of the filter being used.
For example, if a signal is measured at -93 dB in a 10 Hz bandwidth,
then the spectral density would be -103 dB (in a 1 Hz bandwidth). But
make sure that the sweep time in a given RBW = Span / RBW in sec. This
makes it possible to compare noise measurements made with different
bandwidth settings of the spectrum analyzer.