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fir: cleanup halfgen4

This commit is contained in:
Robert Jördens 2016-12-17 21:19:46 +01:00
parent 5f3033b518
commit f310274e39
1 changed files with 10 additions and 6 deletions
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16
artiq/gateware/dsp/fir.py
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@ -1,11 +1,10 @@
from operator import add from operator import add
from functools import reduce from functools import reduce
from collections import namedtuple
import numpy as np import numpy as np
from migen import * from migen import *
def halfgen4(width, n): def halfgen4(width, n, df=1e-3):
""" """
http://recycle.lbl.gov/~ldoolitt/halfband http://recycle.lbl.gov/~ldoolitt/halfband
@ -24,13 +23,18 @@ def halfgen4(width, n):
target = .5*np.ones_like(wfit) target = .5*np.ones_like(wfit)
basis = np.cos(wfit*np.arange(1, 2*n, 2)) basis = np.cos(wfit*np.arange(1, 2*n, 2))
l = np.linalg.pinv(basis)@target
weight = np.ones_like(wfit) weight = np.ones_like(wfit)
f0 = None
for i in range(40): for i in range(40):
err = np.fabs(basis@l - .5)
weight[err > .99*np.max(err)] *= 1 + 1.5/(i + 11)
l = np.linalg.pinv(basis*weight)@(target*weight) l = np.linalg.pinv(basis*weight)@(target*weight)
err = np.fabs(basis@l - .5)
f = np.max(err)/np.mean(err)
if f0 and (f0 - f)/(f0 + f) < df/2:
break
f0 = f
weight[err > (1 - df)*np.max(err)] *= 1 + 1.5/(i + 11)
a = np.c_[l, np.zeros_like(l)].ravel()[:-1] a = np.c_[l, np.zeros_like(l)].ravel()[:-1]
a = np.r_[a[::-1], 1, a]/2 a = np.r_[a[::-1], 1, a]/2
return a return a