1073
Meas Setup
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N dB Points can be used to measure the bandwidth of a signal; it is commonly used in conjunction with a
tracking generator to measure filter bandwidths.
In one of the common use cases, the marker is placed on a peak, and the arrows are displayed N dB down
the skirt from the marker on either side of the peak. The N dB value and the frequency difference
between the two arrows is displayed around the arrow as shown in the figure above. Normally this
displays on the right hand arrow, but if this would place any part of the text off screen to the right then it
displays on the left arrow.
If the test set is unable to find data that is N dB below the marker on either side of the marker, the arrows
are displayed at the indicator point of the marker, no value (---) is displayed as the result and –100 Hz
returned remotely (see figure below):
Some sample N dB scenarios are shown below, to illustrate how the function works in various cases. In
each case, the two-headed blue arrow represents N dB of amplitude.