scipy.signal.buttord

scipy.signal.buttord(wp, ws, gpass, gstop, analog=0)

Butterworth filter order selection.

Return the order of the lowest order digital Butterworth filter that loses no more than gpass dB in the passband and has at least gstop dB attenuation in the stopband.

Parameters:

wp, ws – Passband and stopband edge frequencies, normalized from 0 :

to 1 (1 corresponds to pi radians / sample). For example:

Lowpass: wp = 0.2, ws = 0.3 Highpass: wp = 0.3, ws = 0.2 Bandpass: wp = [0.2, 0.5], ws = [0.1, 0.6] Bandstop: wp = [0.1, 0.6], ws = [0.2, 0.5]

gpass – The maximum loss in the passband (dB). :

gstop – The minimum attenuation in the stopband (dB). :

analog – Non-zero to design an analog filter (in this case wp and :

ws are in radians / second).

Returns:

ord – The lowest order for a Butterworth filter which meets specs. :

Wn – The Butterworth natural frequency (i.e. the “3dB frequency”). :

Should be used with scipy.signal.butter to give filter results.