Added oversampling and sd

Makefile

@@ -12,8 +12,8 @@ FILES = l00_diode \
 	l03_refbias \
 	l04_afe \
 	l05_sc \
-#	l06_adc \
-	l07_vreg \
+	l06_adc \
+#	l07_vreg \
 	l08_pll \
 	l09_osc \
 	l10_lpradio \

ex/sd_1st.py

@@ -4,13 +4,14 @@
 import matplotlib.pyplot as plt
 
 #- Create a time vector
-N = 2**13
-t = np.linspace(0,N,N)
-
+N = 2**12
+#t = np.linspace(0,N,N+1)
+t = np.arange(0,N)
 #- Create the "continuous time" signal
-fbin = 10
+fbin = 47
 fm1 = 1/N*213
 f1 = 1/128 - 1/N
+#f1 = fbin
 fd = fm1
 x_s = np.sin(2*np.pi*f1*t) + + 1/2**15*np.random.randn(N)
 
@@ -21,17 +22,17 @@
 ## Sample
 #- Sampling frequency is 1/nfs of the time vector
 nfs = 4
-x_sn = x_s[0::nfs]
+u = x_s[0::nfs]
 
 bits = 1
-y_sn = np.round(x_sn*2**bits)/2**bits
+y_sn = np.round(u*2**bits)/2**bits
 
 dither = 1
-M = len(x_sn)
+M = len(u)
 y_sd = np.zeros(M)
 x = np.zeros(M)
 for n in range(1,M):
-    x[n] = x[n-1] + (x_sn[n]-y_sd[n-1])
+    x[n] = x[n-1] + (u[n]-y_sd[n-1])
     y_sd[n] = np.round(x[n]*2**bits  + dither*np.random.randn()/4)/2**bits
 
 #- Remove the first samples to get rid of the initial
@@ -53,7 +54,7 @@ def freqDomain(x):
     X = X/np.max(np.abs(X[int(N/4):N-int(N/4)]))
     return X
 X_s = freqDomain(x_s)
-X_sn = freqDomain(x_sn)
+u = freqDomain(u)
 Y_sn = freqDomain(y_sn)
 Y_sdn = freqDomain(y_sd )
 
@@ -63,7 +64,7 @@ def freqDomain(x):
 plt.ylabel("Frequency Domain")
 plt.ylim(-160,0)
 plt.subplot(1,4,2)
-plt.plot(20*np.log10(np.abs(X_sn)))
+plt.plot(20*np.log10(np.abs(u)))
 plt.xlabel("Discrete time, continuous value")
 plt.ylim(-160,0)
 plt.subplot(1,4,3)
@@ -83,4 +84,17 @@ def freqDomain(x):
 fig.set_size_inches(12, 7)
 plt.tight_layout()
 plt.savefig(f"l6_sd_d{dither}_b{bits}.pdf")
+
+
+plt.figure()
+
+NN = int(len(Y_sdn)/2)
+Y_sdn_short = Y_sdn[NN:]
+x_sdn_short = np.arange(0,NN)/NN/2
+plt.semilogx(x_sdn_short,20*np.log10(np.abs(Y_sdn[int(len(Y_sdn)/2):])),color="black")
+plt.xlabel("Normalized frequency")
+plt.ylabel("Magnitude [dB20]")
+plt.grid(True)
+
+plt.savefig(f"l6_sdlog_d{dither}_b{bits}.pdf")
 plt.show()