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Measuring
Low-Level
Signals
Using
Attenuation,
Video
Bandwidth,
and
Video
Averaging
Spectrum analyzer sensitivity is the ability to measure low-level signals. It is
limited by the noise generated inside the spectrum analyzer. The spectrum
analyzer input attenuator and bandwidth settings affect the sensitivity by
changing the signal-to-noise ratio. The attenuator affects the level of a signal
passing through the instrument, whereas the bandwidth affects the level of
internal noise without affecting the signal. In the first two examples in this
section, the attenuator and bandwidth settings are adjusted to view low-level
signals.
If, after adjusting the attenuation and resolution bandwidth, a signal is still
near the noise, visibility can be improved by using the video-bandwidth and
video-averaging functions, as demonstrated in the third and fourth examples.
Example: If a signal is very close to the noise floor, reducing input
attenuation brings the signal out of the noise. Reducing the attenuation to
0
dB
maximizes signal power in the spectrum analyzer.
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