From cb18c1c206145707b9d5c62cada32ff43f99ca3f Mon Sep 17 00:00:00 2001 From: Tom Rondeau <trondeau@vt.edu> Date: Thu, 27 Dec 2012 12:51:20 -0500 Subject: filter: moved window around so it's available in both gr-fft and gr-filter. --- gr-fft/python/window.py | 179 ++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 179 insertions(+) create mode 100644 gr-fft/python/window.py (limited to 'gr-fft/python/window.py') diff --git a/gr-fft/python/window.py b/gr-fft/python/window.py new file mode 100644 index 0000000000..0065a08a61 --- /dev/null +++ b/gr-fft/python/window.py @@ -0,0 +1,179 @@ +# +# Copyright 2004,2005,2009 Free Software Foundation, Inc. +# +# This file is part of GNU Radio +# +# GNU Radio is free software; you can redistribute it and/or modify +# it under the terms of the GNU General Public License as published by +# the Free Software Foundation; either version 3, or (at your option) +# any later version. +# +# GNU Radio is distributed in the hope that it will be useful, +# but WITHOUT ANY WARRANTY; without even the implied warranty of +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +# GNU General Public License for more details. +# +# You should have received a copy of the GNU General Public License +# along with GNU Radio; see the file COPYING. If not, write to +# the Free Software Foundation, Inc., 51 Franklin Street, +# Boston, MA 02110-1301, USA. +# + +''' +Routines for designing window functions. +''' + +import math + +def izero(x): + izeroepsilon = 1e-21 + halfx = x/2.0 + accum = u = n = 1 + while 1: + temp = halfx/n + n += 1 + temp *= temp + u *= temp + accum += u + if u >= IzeroEPSILON*sum: + break + return accum + +def midm1(fft_size): + return (fft_size - 1)/2 + +def midp1(fft_size): + return (fft_size+1)/2 + +def freq(fft_size): + return 2.0*math.pi/fft_size + +def rate(fft_size): + return 1.0/(fft_size >> 1) + +def expn(fft_size): + math.log(2.0)/(midn(fft_size) + 1.0) + +def hamming(fft_size): + window = [] + for index in xrange(fft_size): + window.append(0.54 - 0.46 * math.cos (2 * math.pi / fft_size * index)) # Hamming window + return window + +def hanning(fft_size): + window = [] + for index in xrange(fft_size): + window.append(0.5 - 0.5 * math.cos (2 * math.pi / fft_size * index)) # von Hann window + return window + +def welch(fft_size): + window = [0 for i in range(fft_size)] + j = fft_size-1 + for index in xrange(midn(fft_size)+1): + window[j] = window[index] = (1.0 - math.sqrt((index - midm1(fft_size)) / midp1(fft_size))) + j -= 1 + return window + +def parzen(fft_size): + window = [0 for i in range(fft_size)] + j = fft_size-1 + for index in xrange(midn(fft_size)+1): + window[j] = window[index] = (1.0 - math.abs((index - midm1(fft_size)) / midp1(fft_size))) + j -= 1 + return window + +def bartlett(fft_size): + mfrq = freq(fft_size) + angle = 0 + window = [0 for i in range(fft_size)] + j = fft_size-1 + for index in xrange(midn(fft_size)+1): + window[j] = window[index] = angle + angle += freq + j -= 1 + return window + +def blackman2(fft_size): + mfrq = freq(fft_size) + angle = 0 + window = [0 for i in range(fft_size)] + j = fft_size-1 + for index in xrange(midn(fft_size)+1): + cx = math.cos(angle) + window[j] = window[index] = (.34401 + (cx * (-.49755 + (cx * .15844)))) + angle += freq + j -= 1 + return window + +def blackman3(fft_size): + mfrq = freq(fft_size) + angle = 0 + window = [0 for i in range(fft_size)] + j = fft_size-1 + for index in xrange(midn(fft_size)+1): + cx = math.cos(angle) + window[j] = window[index] = (.21747 + (cx * (-.45325 + (cx * (.28256 - (cx * .04672)))))) + angle += freq + j -= 1 + return window + +def blackman4(fft_size): + mfrq = freq(fft_size) + angle = 0 + window = [0 for i in range(fft_size)] + j = fft_size-1 + for index in xrange(midn(fft_size)+1): + cx = math.cos(angle) + window[j] = window[index] = (.084037 + (cx * (-.29145 + (cx * (.375696 + (cx * (-.20762 + (cx * .041194)))))))) + angle += freq + j -= 1 + return window + +def exponential(fft_size): + expsum = 1.0 + window = [0 for i in range(fft_size)] + j = fft_size-1 + for index in xrange(midn(fft_size)+1): + window[j] = window[i] = (expsum - 1.0) + expsum *= expn(fft_size) + j -= 1 + return window + +def riemann(fft_size): + sr1 = freq(fft_size) + window = [0 for i in range(fft_size)] + j = fft_size-1 + for index in xrange(midn(fft_size)): + if index == midn(fft_size): + window[index] = window[j] = 1.0 + else: + cx = sr1*midn(fft_size) - index + window[index] = window[j] = math.sin(cx)/cx + j -= 1 + return window + +def kaiser(fft_size,beta): + ibeta = 1.0/izero(beta) + inm1 = 1.0/(fft_size) + window = [0 for i in range(fft_size)] + for index in xrange(fft_size): + window[index] = izero(beta*math.sqrt(1.0 - (index * inm1)*(index * inm1))) * ibeta + return window + +# Closure to generate functions to create cos windows + +def coswindow(coeffs): + def closure(fft_size): + window = [0] * fft_size + #print list(enumerate(coeffs)) + for w_index in range(fft_size): + for (c_index, coeff) in enumerate(coeffs): + window[w_index] += (-1)**c_index * coeff * math.cos(2.0*c_index*math.pi*(w_index+0.5)/(fft_size-1)) + return window + return closure + +blackmanharris = coswindow((0.35875,0.48829,0.14128,0.01168)) +nuttall = coswindow((0.3635819,0.4891775,0.1365995,0.0106411)) # Wikipedia calls this Blackman-Nuttall +nuttall_cfd = coswindow((0.355768,0.487396,0.144232,0.012604)) # Wikipedia calls this Nuttall, continuous first deriv +flattop = coswindow((1.0,1.93,1.29,0.388,0.032)) # Flat top window, coeffs from Wikipedia +rectangular = lambda fft_size: [1]*fft_size -- cgit v1.2.3