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#!/usr/bin/env python
#
# Copyright 2004,2005 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 2, 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., 59 Temple Place - Suite 330,
# Boston, MA 02111-1307, USA.
#
from gnuradio import gr, atsc
import math
def main():
fg = gr.flow_graph()
u = gr.file_source(gr.sizeof_float,"/tmp/atsc_pipe_2")
input_rate = 19.2e6
IF_freq = 5.75e6
# 1/2 as wide because we're designing lp filter
symbol_rate = atsc.ATSC_SYMBOL_RATE/2.
NTAPS = 279
tt = gr.firdes.root_raised_cosine (1.0, input_rate, symbol_rate, .115, NTAPS)
# heterodyne the low pass coefficients up to the specified bandpass
# center frequency. Note that when we do this, the filter bandwidth
# is effectively twice the low pass (2.69 * 2 = 5.38) and hence
# matches the diagram in the ATSC spec.
arg = 2. * math.pi * IF_freq / input_rate
t=[]
for i in range(len(tt)):
t += [tt[i] * 2. * math.cos(arg * i)]
rrc = gr.fir_filter_fff(1, t)
fpll = atsc.fpll()
pilot_freq = IF_freq - 3e6 + 0.31e6
lower_edge = 6e6 - 0.31e6
upper_edge = IF_freq - 3e6 + pilot_freq
transition_width = upper_edge - lower_edge
lp_coeffs = gr.firdes.low_pass (1.0,
input_rate,
(lower_edge + upper_edge) * 0.5,
transition_width,
gr.firdes.WIN_HAMMING);
lp_filter = gr.fir_filter_fff (1,lp_coeffs)
alpha = 1e-5
iir = gr.single_pole_iir_filter_ff(alpha)
remove_dc = gr.sub_ff()
out = gr.file_sink(gr.sizeof_float,"/tmp/atsc_pipe_3")
# out = gr.file_sink(gr.sizeof_float,"/mnt/sata/atsc_data_float")
fg.connect(u, fpll, lp_filter)
fg.connect(lp_filter, iir)
fg.connect(lp_filter, (remove_dc,0))
fg.connect(iir, (remove_dc,1))
fg.connect(remove_dc, out)
fg.run()
if __name__ == '__main__':
main ()
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