Relative Bandwidth
Relative Bandwidth : The relative bandwidth (RBW) can be expressed by a number or in terms of octaves or decades. Increasing the frequency of a signal by one octave means doubling its frequency, and by one decade multiplying it by ten. Accordingly, a band-passed signal (or filter) with n octaves or m decades has a ratio between the upper and lower corner frequencies fu/fl = 2n = 10m and a geometric center frequency fo = (fu * fl ) 1/2 = fl * 2n/2 = fl * 10m/2 . From this follows for the relative bandwidth RBW = ( fu - fl )/ fo = (2n - 1)/ 2n/2 = (10m -1)/10m/2. Note that signal and noise amplitudes can be made commensurate only when plotting them in a constant RBW over the whole considered frequency range. (see Chapter 4 of this Manual)
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