Chapter 2 - Window functions (frequency domain)

C2_winfun_freq.py

import numpy as np
from scipy.signal import triang, tukey

import matplotlib.pyplot as plt
import seaborn as sns
sns.set(context='paper',
        style='ticks',
        font_scale=1,
        rc={'figure.figsize': (8, 5),
            'figure.dpi': 100,  # need fixed
            'xtick.direction': 'in',
            'ytick.direction': 'in',
            'axes.linewidth': '1.3',
            'axes.labelsize': 12,
            'xtick.labelsize': 12,
            'ytick.labelsize': 12,
            'savefig.dpi': 300,
            'legend.fontsize': 10,
            # 'text.usetex':True,
             })
plt.figure(figsize=(6,5), dpi=100)
for window, label, c in zip([np.ones(128), triang(128), tukey(128, alpha=0.25), np.hanning(128), np.blackman(128)],
                         ['rectangular', 'triangular', 'Tukey(r=0.25)', 'Hann','Blackman'],
                         ['k', 'b', 'g','r','y']):
    N = 1024
    A = np.fft.fft(window, N)/128*2
    y = np.abs(A)[:N//2] / np.abs(A)[0]
    index = (y ==0)
    y[index] = np.nan
    plt.plot(np.linspace(0,1,N//2),y, label=label, color=c, alpha=0.9)

plt.yscale('log')
plt.xscale('log')
plt.xlim(1e-3,1e-0)
plt.ylim(1e-10,1e-0)
plt.legend()
plt.ylabel('amplitude of leakage')
plt.xlabel('offset from FFT bin center (in units of Nyquist freq)')
plt.grid(which='both',axis='both', linestyle=':')
plt.grid(which='major',axis='both', linestyle='--',c='k',alpha=0.6)
plt.yticks([1e-0,1e-2,1e-4,1e-6,1e-8,1e-10])
plt.xticks([1e-3,1e-2,1e-1,1e-0])
plt.savefig('C2_imags/C2_freq_window.png', dpi=300, bbox_inches='tight')