Compute the attenuation of a Kaiser FIR filter.
Given the number of taps N and the transition width width, compute the attenuation a in dB, given by Kaiser’s formula:
a = 2.285 * (N - 1) * pi * width + 7.95
The number of taps in the FIR filter.
The desired width of the transition region between passband and stopband (or, in general, at any discontinuity) for the filter, expressed as a fraction of the Nyquist frequency.
The attenuation of the ripple, in dB.
Suppose we want to design a FIR filter using the Kaiser window method that will have 211 taps and a transition width of 9 Hz for a signal that is sampled at 480 Hz. Expressed as a fraction of the Nyquist frequency, the width is 9/(0.5*480) = 0.0375. The approximate attenuation (in dB) is computed as follows:
>>> from scipy.signal import kaiser_atten >>> kaiser_atten(211, 0.0375) 64.48099630593983