Filtre elliptique

from scipy import signal
import matplotlib.pyplot as plt
import numpy as np
b, a = signal.ellip(4, 5, 40, 100, 'low', analog=True)
w, h = signal.freqs(b, a)
plt.semilogx(w, 20 * np.log10(abs(h)))
plt.title('Elliptic filter frequency response (rp=5, rs=40)')
plt.xlabel('Frequency [radians / second]')
plt.ylabel('Amplitude [dB]')
plt.margins(0, 0.1)
plt.grid(which='both', axis='both')
plt.axvline(100, color='green') # cutoff frequency
plt.axhline(-40, color='green') # rs
plt.axhline(-5, color='green') # rp
plt.show()
 

from scipy import signal
import matplotlib.pyplot as plt
import numpy as np
N, Wn = signal.ellipord(30, 10, 3, 60, True)
b, a = signal.ellip(N, 3, 60, Wn, 'high', True)
w, h = signal.freqs(b, a, np.logspace(0, 3, 500))
plt.semilogx(w, 20 * np.log10(abs(h)))
plt.title('Elliptical highpass filter fit to constraints')
plt.xlabel('Frequency [radians / second]')
plt.ylabel('Amplitude [dB]')
plt.grid(which='both', axis='both')
plt.fill([.1, 10,  10,  .1], [1e4, 1e4, -60, -60], '0.9', lw=0) # stop
plt.fill([30, 30, 1e9, 1e9], [-99,  -3,  -3, -99], '0.9', lw=0) # pass
plt.axis([1, 300, -80, 3])
plt.show()