[英]Python, FFT and DC offset analysis
我在占空比為 50% 的方波信號(100Hz,0V-5V)上測試 FFT,但我不明白為什么我的 DC 偏移量很大?
理論上應該是2.5V?
謝謝,最好的問候。
基波正常,其他諧波正確。
from scipy.fftpack import fft
from scipy import signal
import matplotlib.pyplot as plt
import numpy as np
#
# configuration
# time analyse = L * (1/Fsample)
#
L = 512 # lenght buffer
Fsample = 2000 # frequency sample
Fsignal = 100 # frequency
#********************************
# perdiode sample
Tsample = 1.0/Fsample
# time vector, start = 0s, stop = 0.1024s, step = (0.1024s / (1/Fe))
t = np.linspace(0.0, L*Tsample, L)
# signal definition, DC offet = 2.5V, Amplitude = 2.5V
signal = 2.5 + 2.5*signal.square(2 * np.pi * Fsignal * t, 0.5)
# plot time signal
plt.subplot(2,1,1)
plt.plot(t, signal)
# fft of time signal
yf = fft(signal)
# time vector of fft
xf = np.linspace(0.0, 1.0/(2.0*Tsample), L//2)
# plot spectral
plt.subplot(2,1,2)
plt.plot(xf, 2.0/L * np.abs(yf[0:L//2]))
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