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#
# Copyright 2006 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., 51 Franklin Street,
# Boston, MA 02110-1301, USA.
#
from gnuradio import gr, optfir
from math import pi
import pager_swig
class flex_demod(gr.hier_block):
"""
FLEX protocol demodulation block.
This block demodulates a band-limited, complex down-converted baseband
channel into FLEX protocol frames.
Flow graph (so far):
QUAD - Quadrature demodulator converts FSK to baseband amplitudes
LPF - Low pass filter to remove noise prior to slicer
SLICER - Converts input to one of four symbols (0, 1, 2, 3)
DEFRAMER - Syncronizes symbol stream and outputs FLEX codewords
---
@param fg: flowgraph
@param channel_rate: incoming sample rate of the baseband channel
@type sample_rate: integer
"""
def __init__(self, fg, channel_rate):
k = channel_rate/(2*pi*4800) # 4800 Hz max deviation
QUAD = gr.quadrature_demod_cf(k)
taps = optfir.low_pass(1.0, channel_rate, 3200, 6400, 0.1, 60)
LPF = gr.fir_filter_fff(1, taps)
SLICER = pager_swig.slicer_fb(.001, .00001) # Attack, decay
DEFRAMER = pager_swig.flex_deframer(channel_rate)
fg.connect(QUAD, LPF, SLICER, DEFRAMER)
gr.hier_block.__init__(self, fg, QUAD, DEFRAMER)
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