add demodulation simulation

demod_sim.py

@@ -0,0 +1,25 @@
+import numpy as np
+import matplotlib.pyplot as plt
+
+fs = 5e6
+fref = 1e6
+ascan = 2e-3/633e-9
+fscan = 50.0
+leakage = 0.2
+
+
+t = np.arange(0.0, 0.1, 1/fs)
+ref = np.exp(2.0j*np.pi*fref*t)
+position = ascan*np.sin(2.0*np.pi*fscan*t)
+meas = np.exp(2.0j*np.pi*(fref*t + position)) + leakage*ref
+
+
+demod = np.conjugate(ref)*meas
+estimated_leakage = np.real(np.sum(demod)/len(demod))
+estimated_position = np.unwrap(np.angle(demod - estimated_leakage))/(2.0*np.pi)
+
+
+print(estimated_leakage)
+plt.plot(estimated_position)
+plt.plot(position)
+plt.show()