simulating CIC filter and modified one in python

cictest-mod.py

#!/usr/bin/env python
import numpy as np
from pylab import *

x = np.random.randn(65536)

m=16
d0 = [0] * m
d1 = [0] * m
d2 = [0] * m
y = []
s0 = 0
s1 = 0
s2 = 0
x.shape = (len(x)/2,2)
for xi in x:
    s0 += xi[0]+xi[1]
    s1 += s0
    s2 += s1
    d0.append(s2)
    d1.append(d0.pop(0) - d0[-1])
    d2.append(d1.pop(0) - d1[-1])
    y.append(d2.pop(0) - d2[-1])

psd(y)
show()

cictest.py

#!/usr/bin/env python
import numpy as np
from pylab import *

x = np.random.randn(65536)

m=16
d0 = [0] * m
d1 = [0] * m
d2 = [0] * m
y = []
s0 = 0
s1 = 0
s2 = 0
for xi in x:
    s0 += xi
    s1 += s0
    s2 += s1
    d0.append(s2)
    d1.append(d0.pop(0) - d0[-1])
    d2.append(d1.pop(0) - d1[-1])
    y.append(d2.pop(0) - d2[-1])

psd(y)
show()

CIC

modified CIC