Нужно разобраться в коде

N_FFT = float(len(y))
f = np.arange(0,Fs/2,Fs/N_FFT)
w = np.hanning(len(y))
y_f = np.fft.fft(np.multiply(y,w))
y_f = 10*np.log10(np.abs(y_f[0:N_FFT/2]/N_FFT))

import numpy as np
import pylab as pl
import scipy.signal.signaltools as sigtool
import scipy.signal as signal
from numpy.random import sample
 
#the following variables setup the system
Fc = 1000       #simulate a carrier frequency of 1kHz
Fbit = 50       #simulated bitrate of data
Fdev = 500      #frequency deviation, make higher than bitrate
N = 64          #how many bits to send
A = 1           #transmitted signal amplitude
Fs = 10000      #sampling frequency for the simulator, must be higher than twice the carrier frequency
A_n = 0.1       #noise peak amplitude
N_prntbits = 10 #number of bits to print in plots
 
def plot_data(y):
    #view the data in time and frequency domain
    #calculate the frequency domain for viewing purposes
    N_FFT = float(len(y))
    f = np.arange(0,Fs/2,Fs/N_FFT)
    w = np.hanning(len(y))
    y_f = np.fft.fft(np.multiply(y,w))
    y_f = 10*np.log10(np.abs(y_f[0:N_FFT/2]/N_FFT))
    pl.subplot(3,1,1)
    pl.plot(t[0:Fs*N_prntbits/Fbit],m[0:Fs*N_prntbits/Fbit])
    pl.xlabel('Time (s)')
    pl.ylabel('Frequency (Hz)')
    pl.title('Original VCO output versus time')
    pl.grid(True)
    pl.subplot(3,1,2)
    pl.plot(t[0:Fs*N_prntbits/Fbit],y[0:Fs*N_prntbits/Fbit])
    pl.xlabel('Time (s)')
    pl.ylabel('Amplitude (V)')
    pl.title('Amplitude of carrier versus time')
    pl.grid(True)
    pl.subplot(3,1,3)
    pl.plot(f[0:(Fc+Fdev*2)*N_FFT/Fs],y_f[0:(Fc+Fdev*2)*N_FFT/Fs])
    pl.xlabel('Frequency (Hz)')
    pl.ylabel('Amplitude (dB)')
    pl.title('Spectrum')
    pl.grid(True)
    pl.tight_layout()
    pl.show()