如何過濾fft輸出以刪除0 Hz分量

我試圖計算實驗數據集的傅里葉變換。我最終看到0 Hz分量更高的數據。任何想法如何消除這一點？ 0赫茲組件實際代表什麼？如何過濾fft輸出以刪除0 Hz分量

#Program for Fourier Transformation 
# last update 131003, aj 
import numpy as np 
import numpy.fft as fft 
import matplotlib.pyplot as plt 

def readdat(filename): 
    """ 
     Reads experimental data from the file 
    """ 

    # read all lines of input files 
    fp = open(filename, 'r') 
    lines = fp.readlines() # to read the tabulated data 
    fp.close() 

    # Processing the file data 
    time = [] 
    ampl = [] 
    for line in lines: 
     if line[0:1] == '#': 
      continue # ignore comments in the file 
     try: 
      time.append(float(line.split()[0])) 
      #first column is time 
      ampl.append(float(line.split()[1])) 
      # second column is corresponding amplitude 
     except: 
      # if the data interpretation fails.. 
      continue 
    return np.asarray(time), np.asarray(ampl) 

if __name__ == '__main__': 

    time, ampl = readdat('VM.dat') 
    print time 
    print ampl 

    spectrum = fft.fft(ampl) 
    # assume samples at regular intervals 
    timestep = time[1]-time[0] 
    freq = fft.fftfreq(len(spectrum),d=timestep) 
    freq=fft.fftshift(freq) 
    spectrum = fft.fftshift(spectrum) 
    plt.figure(figsize=(5.0*1.21,5.0)) 
    plt.plot(freq,spectrum.real) 
    plt.title("Measured Voltage") 
    plt.xlabel("frequency(rad/s)") 
    plt.ylabel("Spectrum") 
    plt.xlim(0.,5.) 
    plt.ylim(ymin=0.) 
    plt.grid() 
    plt.savefig("VM_figure.png")

來源

2013-10-09 user2288393