Post subject: How to measure Phase Noise and Power Spectral
Unread postPosted: Thu Dec 30, 2004 5:04 am
to measure Phase Noise (dBc/Hz) and Power Spectral Density (dBm/Hz)
using Spectrum Analyzer?
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 vs. Frequency.
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
postPosted: 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