VBW (Actual)
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This parameter is only available when the active Input Domain is Time and when doing Power Spectrum, Adjacent Channel Power and Spectral Emissions Mask measurements.
displays the actual video bandwidth (VBW). Actual VBW may be different from the desired VBW is when gating is used and the gate length is longer than what is needed by the current RBW Resolution Band Width (RBW or ResBW): specifies the minimum frequency bandwith that two separate frequency spectra can be resolved and viewed seperately. For FFT (digital) based VSA's the process is equivalent to passing a time-domain signal through a bank of bandpass filters, whose center frequencies correspond to the frequencies of the FFT bins. For a traditional swept-tuned (non-digital) spectrum analyzer, the resolution bandwidth is the bandwidth of the IF filter which determines the selectivity./VBW ratio (in which case the gate length is prioritized, resulting in a different actual VBW value instead of the desired VBW value).
The VBW value shown at the bottom of some traces (e.g., Spectrum) is the Actual VBW value (not the desired VBW value).
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