Download AFG-3000 Series User Manual

An Introduction to Spectrum Analyzers
Figure B-8 shows how the VBW affects the displayed
output. If the signal under test passes through two different
VBW filters, in which VBW1 is less than VBW2, we can see that
the magnitude of the noise floor of VBW2 is greater than that in
VBW1. But notice that the average level of the noise floor
remains the same. The VBW filter only averages the noise level;
It doesn’t affect the overall amplitude of the signal noise floor.
Figure B-8.
Different VBWs
Signal under
VBW
Results
Noise
VBW1
VBW2
27