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#!/usr/bin/env python
#
# Copyright 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.
#
from gnuradio import gr, blks2
import sys, time
try:
import scipy
from scipy import fftpack
except ImportError:
print "Error: Program requires scipy (see: www.scipy.org)."
sys.exit(1)
try:
import pylab
from pylab import mlab
except ImportError:
print "Error: Program requires matplotlib (see: matplotlib.sourceforge.net)."
sys.exit(1)
class pfb_top_block(gr.top_block):
def __init__(self):
gr.top_block.__init__(self)
self._N = 10000000 # number of samples to use
self._fs = 10000 # initial sampling rate
self._decim = 20 # Decimation rate
# Generate the prototype filter taps for the decimators with a 200 Hz bandwidth
self._taps = gr.firdes.low_pass_2(1, self._fs, 200, 150,
attenuation_dB=120, window=gr.firdes.WIN_BLACKMAN_hARRIS)
# Calculate the number of taps per channel for our own information
tpc = scipy.ceil(float(len(self._taps)) / float(self._decim))
print "Number of taps: ", len(self._taps)
print "Number of filters: ", self._decim
print "Taps per channel: ", tpc
# Build the input signal source
# We create a list of freqs, and a sine wave is generated and added to the source
# for each one of these frequencies.
self.signals = list()
self.add = gr.add_cc()
freqs = [10, 20, 2040]
for i in xrange(len(freqs)):
self.signals.append(gr.sig_source_c(self._fs, gr.GR_SIN_WAVE, freqs[i], 1))
self.connect(self.signals[i], (self.add,i))
self.head = gr.head(gr.sizeof_gr_complex, self._N)
# Construct a PFB decimator filter
self.pfb = blks2.pfb_decimator_ccf(self._decim, self._taps, 0)
# Construct a standard FIR decimating filter
self.dec = gr.fir_filter_ccf(self._decim, self._taps)
self.snk_i = gr.vector_sink_c()
# Connect the blocks
self.connect(self.add, self.head, self.pfb)
self.connect(self.add, self.snk_i)
# Create the sink for the decimated siganl
self.snk = gr.vector_sink_c()
self.connect(self.pfb, self.snk)
def main():
tb = pfb_top_block()
tstart = time.time()
tb.run()
tend = time.time()
print "Run time: %f" % (tend - tstart)
if 1:
fig1 = pylab.figure(1, figsize=(16,9))
fig2 = pylab.figure(2, figsize=(16,9))
Ns = 10000
Ne = 10000
fftlen = 8192
winfunc = scipy.blackman
fs = tb._fs
# Plot the input to the decimator
d = tb.snk_i.data()[Ns:Ns+Ne]
sp1_f = fig1.add_subplot(2, 1, 1)
X,freq = mlab.psd(d, NFFT=fftlen, noverlap=fftlen/4, Fs=fs,
window = lambda d: d*winfunc(fftlen),
scale_by_freq=True)
X_in = 10.0*scipy.log10(abs(fftpack.fftshift(X)))
f_in = scipy.arange(-fs/2.0, fs/2.0, fs/float(X_in.size))
p1_f = sp1_f.plot(f_in, X_in, "b")
sp1_f.set_xlim([min(f_in), max(f_in)+1])
sp1_f.set_ylim([-200.0, 50.0])
sp1_f.set_title("Input Signal", weight="bold")
sp1_f.set_xlabel("Frequency (Hz)")
sp1_f.set_ylabel("Power (dBW)")
Ts = 1.0/fs
Tmax = len(d)*Ts
t_in = scipy.arange(0, Tmax, Ts)
x_in = scipy.array(d)
sp1_t = fig1.add_subplot(2, 1, 2)
p1_t = sp1_t.plot(t_in, x_in.real, "b")
p1_t = sp1_t.plot(t_in, x_in.imag, "r")
sp1_t.set_ylim([-tb._decim*1.1, tb._decim*1.1])
sp1_t.set_xlabel("Time (s)")
sp1_t.set_ylabel("Amplitude")
# Plot the output of the decimator
fs_o = tb._fs / tb._decim
sp2_f = fig2.add_subplot(2, 1, 1)
d = tb.snk.data()[Ns:Ns+Ne]
X,freq = mlab.psd(d, NFFT=fftlen, noverlap=fftlen/4, Fs=fs_o,
window = lambda d: d*winfunc(fftlen),
scale_by_freq=True)
X_o = 10.0*scipy.log10(abs(fftpack.fftshift(X)))
f_o = scipy.arange(-fs_o/2.0, fs_o/2.0, fs_o/float(X_o.size))
p2_f = sp2_f.plot(f_o, X_o, "b")
sp2_f.set_xlim([min(f_o), max(f_o)+1])
sp2_f.set_ylim([-200.0, 50.0])
sp2_f.set_title("PFB Decimated Signal", weight="bold")
sp2_f.set_xlabel("Frequency (Hz)")
sp2_f.set_ylabel("Power (dBW)")
Ts_o = 1.0/fs_o
Tmax_o = len(d)*Ts_o
x_o = scipy.array(d)
t_o = scipy.arange(0, Tmax_o, Ts_o)
sp2_t = fig2.add_subplot(2, 1, 2)
p2_t = sp2_t.plot(t_o, x_o.real, "b-o")
p2_t = sp2_t.plot(t_o, x_o.imag, "r-o")
sp2_t.set_ylim([-2.5, 2.5])
sp2_t.set_xlabel("Time (s)")
sp2_t.set_ylabel("Amplitude")
pylab.show()
if __name__ == "__main__":
try:
main()
except KeyboardInterrupt:
pass
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