VLSI Lab 3 rev. 1

7th-Semester-Fall-2024/ECOMMS/labs/lab2/am.py

@@ -0,0 +1,53 @@
+import numpy as np
+import matplotlib.pyplot as plt
+import scipy as sp
+
+
+def lowpass(data, f_cutoff, f_s):
+    nyq = 0.5*f_s
+    normal_cutoff = f_cutoff/nyq
+    b, a = sp.signal.butter(1, normal_cutoff, btype="low", analog=False)
+    y = sp.signal.lfilter(b, a, data)
+    return y
+
+def dsb_am(m, f_c, t):
+    omega_c = 2*np.pi*f_c
+    c = np.cos(omega_c*t)
+    return 0.5*m*c + c
+
+def dsb_sc(m, f_c, t):
+    omega_c = 2*np.pi*f_c
+    c = np.cos(omega_c*t)
+    return 0.5*m*c
+
+def product_demod(s, f_baseband, f_c, f_s, t):
+    omega_c = 2*np.pi*f_c
+    mixed = s*np.cos(omega_c*t)
+    return lowpass(mixed, f_baseband, f_s)
+
+def main():
+    T_s = 0.0005
+    f_s = 1/T_s
+
+    f_m = 10
+    omega_m = 2*np.pi*f_m
+
+    f_c = 100
+
+    t = np.arange(0,1,T_s)
+    f = np.linspace(0,f_s,len(t))
+
+    m = np.sin(omega_m*t) + np.sin(omega_m/2*t)
+    s_am = dsb_am(m, f_c, t)
+    s_sc = dsb_sc(m, f_c, t)
+    m_am_demod = product_demod(s_am, f_m, f_c, f_s, t)
+    m_sc_demod = product_demod(s_sc, f_m, f_c, f_s, t)
+
+    plt.plot(t, m, label="Original Message Signal")
+    plt.plot(t, m_am_demod, label="Demodulated DSB-AM Signal")
+    plt.plot(t, m_sc_demod, label="Demodulated DSB-SC Signal")
+    plt.legend(loc="upper right")
+    plt.show()
+
+if __name__ == "__main__":
+    main()