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Making Basic Measurements Using Spectrum Analyzer Mode
Measuring low-level Signals Using Attenuation, Video Bandwidth, and Video Averaging
Example: If a signal level is very close to the noise floor, video averaging is
another way to make the signal more visible.
NOTE
The time required to construct a full trace that is averaged to the desired degree is approximately the
same when using either the video-bandwidth or the video-averaging technique. The video bandwidth
technique completes the averaging as a slow sweep is taken, whereas the video averaging technique
takes many sweeps to complete the average. Characteristics of the signal being measured such as drift
and duty cycle determine which technique is appropriate.
Video averaging is a digital process in which each trace point is averaged
with the previous trace-point average. Selecting video averaging changes
the detection mode from peak to sample. The result is a sudden drop in the
displayed noise level. The sample mode displays the instantaneous value of
the signal at the end of the time or frequency interval represented by each
display point, rather than the value of the peak during the interval. Sample
mode is not used to measure signal amplitudes accurately because it may not
find the true peak of the signal.
Video averaging
clariEes
low-level signals in wide bandwidths by averaging
the signal and the noise. As the spectrum analyzer takes sweeps, you can
watch video averaging smooth the trace.
1. Position a low-level signal on the spectrum analyzer screen.
2. Press
(-1,
More 1 of 3 , then VID AVG
OM
OFF . When ON is
underlined, the video-averaging routine is initiated. As the averaging
routine smooths the trace, low-level signals become more visible. VID AVG
100 appears in the active function block.
The number represents the number of samples (or sweeps) taken to
complete the averaging routine.
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