Numpy 中的 kaiser – Python

Kaiser 窗是使用 Bessel函数形成的锥度。

Syntax : numpy.kaiser(M, beta)

Parameters :
M : [int] Number of points in the output window. If zero or less, an empty array is returned.
beta : [float] Shape parameter for window.

Returns:
out : [array] The window, with the maximum value normalized to one (the value one appears only if the number of samples is odd).

例子：

import numpy as np 
    
print(np.kaiser(12, 14)) 

输出：

[  7.72686684e-06   3.46009194e-03   4.65200189e-02   2.29737120e-01
   5.99885316e-01   9.45674898e-01   9.45674898e-01   5.99885316e-01
   2.29737120e-01   4.65200189e-02   3.46009194e-03   7.72686684e-06]

绘制窗口及其频率响应 –

对于窗口：

import numpy as np 
import matplotlib.pyplot as plt 
from numpy.fft import fft, fftshift 
   
window = np.kaiser(51, 14)
   
plt.plot(window) 
plt.title("Kaiser window")
plt.ylabel("Amplitude") 
plt.xlabel("Sample") 
plt.show() 

输出：

对于频率：

import numpy as np 
import matplotlib.pyplot as plt 
from numpy.fft import fft, fftshift 
    
window = np.kaiser(51, 14)
plt.figure() 
    
A = fft(window, 2048) / 25.5
mag = np.abs(fftshift(A)) 
freq = np.linspace(-0.5, 0.5, len(A)) 
response = 20 * np.log10(mag) 
response = np.clip(response, -100, 100) 
    
plt.plot(freq, response) 
plt.title("Frequency response of Kaiser window") 
plt.ylabel("Magnitude [dB]") 
plt.xlabel("Normalized frequency [cycles per sample]") 
plt.axis("tight") 
plt.show() 

输出：