898
BW
The figure below shows the relationships of the various filter bandwidths for filters with the X-Series’
shape factor (shape factor is defined as the ratio of the –60 dB bandwidth to the – 3 dB bandwidth):
The Filter Type menu lets you choose the filter bandwidth (–3 dB, –6 dB, Noise or Impulse) that is used
when specifying the width of the filter. Note that for a given Gaussian filter, changing the filter
bandwidth specification does not affect the filter width at all but only the means of specifying it. For
example, the filter whose –3 dB bandwidth is 1.0 kHz is the same as the filter whose –6 dB bandwidth is
1.41 kHz, whose Noise bandwidth is 1.06 kHz, and whose Impulse bandwidth is 1.48 kHz. As you cycle
through these various filter bandwidths the filter does not change, but the way the filter is annotated and
the value which appears in the active function area and on the key does.
–3 dB (Normal)
Selects the normal gaussian-shaped bandwidths that are defined by their –3 dB bandwidths.
Key Path BW, RBW Control, Filter BW
Example BAND:TYPE DB3
-3 dB BW = B3
-60 dB BW = 4.472 * B3
-6 dB BW = 1.414* B3
Impulse BW = 1.505 * B3
Noise BW = 1.065 * B3
-6 dB
-3 dB
0 dB