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#
# Copyright 2006,2007,2012 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
from gnuradio import blocks
from gnuradio import filter
class am_demod_cf(gr.hier_block2):
"""
Generalized AM demodulation block with audio filtering.
This block demodulates a band-limited, complex down-converted AM
channel into the the original baseband signal, applying low pass
filtering to the audio output. It produces a float stream in the
range [-1.0, +1.0].
Args:
channel_rate: incoming sample rate of the AM baseband (integer)
audio_decim: input to output decimation rate (integer)
audio_pass: audio low pass filter passband frequency (float)
audio_stop: audio low pass filter stop frequency (float)
"""
def __init__(self, channel_rate, audio_decim, audio_pass, audio_stop):
gr.hier_block2.__init__(self, "am_demod_cf",
gr.io_signature(1, 1, gr.sizeof_gr_complex), # Input signature
gr.io_signature(1, 1, gr.sizeof_float)) # Input signature
MAG = blocks.complex_to_mag()
DCR = blocks.add_const_ff(-1.0)
audio_taps = filter.optfir.low_pass(0.5, # Filter gain
channel_rate, # Sample rate
audio_pass, # Audio passband
audio_stop, # Audio stopband
0.1, # Passband ripple
60) # Stopband attenuation
LPF = filter.fir_filter_fff(audio_decim, audio_taps)
self.connect(self, MAG, DCR, LPF, self)
class demod_10k0a3e_cf(am_demod_cf):
"""
AM demodulation block, 10 KHz channel.
This block demodulates an AM channel conformant to 10K0A3E emission
standards, such as broadcast band AM transmissions.
Args:
channel_rate: incoming sample rate of the AM baseband (integer)
audio_decim: input to output decimation rate (integer)
"""
def __init__(self, channel_rate, audio_decim):
am_demod_cf.__init__(self, channel_rate, audio_decim,
5000, # Audio passband
5500) # Audio stopband
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