import numpy as np
import matplotlib.pyplot as plt

plt.rcParams["figure.figsize"] = [7.00, 3.50]
plt.rcParams["figure.autolayout"] = True

N = 256
t = np.arange(N)
m = 4
nu = float(m)/N

signal = np.sin(2*np.pi*nu*t)

ft = np.fft.fft(signal)

freq = np.fft.fftfreq(N)

plt.plot(freq, ft.real**2+ft.imag**2)

plt.show()