Шаг в графике

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 = 100  # simulate a carrier frequency of 1kHz
Fbit = 50  # simulated bitrate of data
Fdev = 50  # frequency deviation, make higher than bitrate
N = 64  # how many bits to send
A = 1  # transmitted signal amplitude
Fs = 1000  # sampling frequency for the simulator, must be higher than twice the carrier frequency
A_n = 0.10  # 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)  
    y_f = np.fft.fft(y)
    pl.figure(figsize=(17, 7))
 
    pl.subplot(3, 1, 3)
    pl.plot(f[0: int(Fc + Fdev * 2 * N_FFT / Fs)], y_f[0:int(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()
 
 
"""
Data in
"""
data_in = np.loadtxt("2.txt",delimiter='\r\n', dtype=np.float)
N = N_prntbits = len(data_in)
 
"""
VCO
"""
t = np.arange(0, float(N) / float(Fbit), 1 / float(Fs),
              dtype=np.float)  
 
# extend the data_in to account for the bitrate and convert 0/1 to frequency
m = np.zeros(0).astype(float)
for bit in data_in:
    
    if bit == 1:
        m = np.hstack((m, np.multiply(np.ones(Fs // Fbit), Fc + Fdev)))
    else:
        m = np.hstack((m, np.multiply(np.ones(Fs // Fbit), Fc - Fdev)))
# calculate the output of the VCO
y = np.zeros(0)  
y = A * np.cos(2 * np.pi * np.multiply(m, t))  
plot_data(y)