Simulation of some modulation techniques using Python.

Modulation.py

import matplotlib.pyplot as plt
from numpy import arange, cos, sin, fft
from math import pi
from scipy.signal import hilbert

# Givens
t = arange(0, 1e-2, 1/2e4)
f = fft.fftfreq(t.shape[-1])
f_m, f_c = 1e3, 1e6
A_c = 10
modulatingSignal = cos(2*pi*f_m*t)


# DSB-SC
unmodulatedCarrier = A_c*cos(2*pi*t*f_c)
modulatedSignal = modulatingSignal*unmodulatedCarrier
spectrum = fft.fft(modulatedSignal)
plt.plot(f, spectrum.real, f, spectrum.imag)
plt.title('Spectrum of the DSB-SC modulated signal')
plt.show()
line1, = plt.plot(t, modulatingSignal, 'r')
line2, = plt.plot(t, modulatedSignal, 'b')
plt.legend((line1, line2), ('modulating signal','modulated signal'))
plt.title('Double Side Band Suppressed Carrier')
plt.show()

# DSB-LC
modulatedSignal = (A_c + modulatingSignal)*cos(2*pi*t*f_c)
spectrum = fft.fft(modulatedSignal)
plt.plot(f, spectrum.real, f, spectrum.imag)
plt.title('Spectrum of the DSB-LC modulated signal')
plt.show()
line1, = plt.plot(t, modulatingSignal, 'r')
line2, = plt.plot(t, modulatedSignal, 'b')
plt.legend((line1, line2), ('modulating signal','modulated signal'))
plt.title('Double Side Band Large Carrier')
plt.show()

# SSB 
modulatingSignal_h = hilbert(modulatingSignal)
USB = modulatingSignal*cos(2*pi*f_c*t) - modulatingSignal_h*sin(2*pi*f_c*t)
LSB = modulatingSignal*cos(2*pi*f_c*t) + modulatingSignal_h*sin(2*pi*f_c*t)
    # Frequency Domain
specFig = plt.figure()
plt.title('Single Side Band Spectrum')
u_spectrum = fft.fft(USB)
ax0 = specFig.add_subplot(211)
ax0.plot(f, u_spectrum.real, f, u_spectrum.imag)
l_spectrum = fft.fft(LSB)
ax1 = specFig.add_subplot(212)
ax1.plot(f, l_spectrum.real, f, l_spectrum.imag)
    # Time Domain
fig = plt.figure()
plt.title('Single Side Band')
ax0 = fig.add_subplot(211)
ax0.plot(t, USB, 'y', label='USB')
ax0.legend()
ax1 = fig.add_subplot(212)
ax1.plot(t, LSB, 'c', label='LSB')
ax1.legend()
plt.show()

# FM and PM
b = 3       # modulation index
modulatedSignal = A_c*cos(f_c*t + b*sin(f_m*t))
spectrum = fft.fft(modulatedSignal)
plt.plot(f, spectrum.real, f, spectrum.imag)
plt.title('Spectrum of the frequency modulated signal')
plt.show()
plt.plot(t, modulatedSignal, 'g')
plt.title('Frequency Modulation')
plt.show()

Here is a description of the implemented modulation techniques.