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Diffstat (limited to 'gnuradio-core/src/examples/pfb/decimate.py')
| -rwxr-xr-x | gnuradio-core/src/examples/pfb/decimate.py | 178 |
1 files changed, 178 insertions, 0 deletions
diff --git a/gnuradio-core/src/examples/pfb/decimate.py b/gnuradio-core/src/examples/pfb/decimate.py new file mode 100755 index 000000000..643a2c241 --- /dev/null +++ b/gnuradio-core/src/examples/pfb/decimate.py @@ -0,0 +1,178 @@ +#!/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 + |