resolution bandwidth: The resolution bandwidth filter or rbw filter is the bandpass filter in the if path. Adjusting the bandwidth of this filter allows for the discrimination of signals with closely spaced frequency components, while also changing the measured noise floor. Decreasing the bandwidth of rbw filter decreases the measured noise floor and vice-versa. This is due to higher rbw filters passing more frequency components through to the envelope detector than a lower bandwidth rbw filters, therefore a higher rbw causes a higher measured noise floor.
Video bandwidth: The video bandwidth filter or vbw filter is the low-pass filter directly after the envelope detector. This filter is used to “smooth” the display by removing noise from the envelope. Similar to the rbw, the vbw affects the sweep time of the display if the vbw is less than the rbw. If vbw is less than rbw, this relation for sweep time is useful:
where st is sweep time in seconds, k is proportionality constant, span is the frequency range under consideration in hertz, rbw is the resolution bandwidth in hertz, and vbw is the video bandwidth in hertz.
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spectrum analysis application notes | agilent
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