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scipy.signal.cheb2ord

scipy.signal.cheb2ord(wp, ws, gpass, gstop, analog=0)

Chebyshev type II filter order selection.

Description:

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

Parameters :

wp, ws : float

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 : float

The maximum loss in the passband (dB).

gstop : float

The minimum attenuation in the stopband (dB).

analog : int, optional

Non-zero to design an analog filter (in this case wp and ws are in radians / second).

Returns :

ord : int

The lowest order for a Chebyshev type II filter that meets specs.

wn : ndarray or float

The Chebyshev natural frequency (the “3dB frequency”) for use with cheby2 to give filter results.