數字濾波分為 IIR 濾波，和FIR 濾波。

FIR 濾波：

import scipy.signal as signal
import numpy as np
import pylab as pl
import matplotlib.pyplot as plt
import matplotlib
from scipy import signal
b = signal.firwin(80,0.5,window=('kaiser',8))
w,h = signal.freqz(b)
 
import matplotlib.pyplot as plt
fig,ax1 = plt.subplots()
ax1.set_title('Digital filter frequency response')
 
ax1.plot(w,20 * np.log10(abs(h)),'b')
ax1.set_ylabel('Amplitude [dB]',color='b')
ax1.set_xlabel('Frequency [rad/sample]')
 
ax2 = ax1.twinx()
angles = np.unwrap(np.angle(h))
ax2.plot(w,angles,'g')
ax2.set_ylabel('Angle (radians)',color='g')
ax2.grid()
ax2.axis('tight')
plt.show()

執行結果：

IIR 濾波器：

from scipy import signal
import matplotlib.pyplot as plt
import matplotlib.ticker
import numpy as np
# 藍色的是頻譜圖，綠色的是相點陣圖
wp = 0.2
ws = 0.3
gpass = 1
gstop = 40
system = signal.iirdesign(wp,ws,gpass,gstop)
w,h = signal.freqz(*system)
fig,ax1 = plt.subplots()
ax1.set_title('Digital filter frequency response')
ax1.plot(w,color='b')
ax1.set_xlabel('Frequency [rad/sample]')
ax1.grid()
ax1.set_ylim([-110,10])
 
nticks = 8
ax1.yaxis.set_major_locator(matplotlib.ticker.LinearLocator(nticks))
 
plt.show()

執行結果：

IIR 濾波器中cheyb2 濾波器的運用

from  scipy import signal
import matplotlib.pyplot as plt
import numpy as np
b,a = signal.cheby2(4,40,100,'low',analog=True)
w,h = signal.freqs(b,a)
plt.semilogx(w,20 * np.log10(abs(h)))#用於繪製折線圖，兩個函式的 x 軸、y 軸分別是指數型的。
#plt.plot(w,20 * np.log10(abs(h)))
plt.title('Chebyshev Type II frequency response (rs=40)')
plt.xlabel('Frequency [radians / second]')
plt.ylabel('Amplitude [dB]')
plt.margins(0,0.1)#  not sure
plt.grid(which='both',axis='both')
 
t = np.linspace(0,1,1000,False) # 1 second
sig = np.sin(2*np.pi*10*t) + np.sin(2*np.pi*20*t)
fig,(ax1,ax2) = plt.subplots(2,sharex=True)
ax1.plot(t,sig)
ax1.set_title('10 Hz and 20 Hz sinusoids')
ax1.axis([0,-2,2])
 
sos = signal.cheby2(12,20,17,'hp',fs=1000,output='sos')
filtered = signal.sosfilt(sos,sig)
ax2.plot(t,filtered)
ax2.set_title('After 17 Hz high-pass filter')
ax2.axis([0,2])
ax2.set_xlabel('Time [seconds]')
 
plt.show()

以上這篇python 經典數字濾波例項就是小編分享給大家的全部內容了，希望能給大家一個參考，也希望大家多多支援我們。