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# Copyright 2011 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.
#
# This tries to push the hilbert transform for ssb demod back into the
# freq. xlating filter.
#
# The starting point for this was weaver_isb_am1_usrp3.py.
#
# The tap coefficients for freq_xlating_fir_filter_ccf were generated
# externally and are read from a file because I didn't want to learn how
# to make fir filters with arbitrary phase response using python numeric
# facilities.
#
# They were generated using Scilab which I am already familiar with.
# M. Revnell Jan 06
from gnuradio import gr
class ssb_demod( gr.hier_block2 ):
def __init__( self, if_rate, af_rate ):
gr.hier_block2.__init__(self, "ssb_demod",
gr.io_signature(1,1,gr.sizeof_gr_complex),
gr.io_signature(1,1,gr.sizeof_float))
self.if_rate = int(if_rate)
self.af_rate = int(af_rate)
self.if_decim = int(if_rate / af_rate)
self.sideband = 1
self.xlate_taps = ([complex(v) for v in file('ssb_taps').readlines()])
self.audio_taps = gr.firdes.low_pass(
1.0,
self.af_rate,
3e3,
600,
gr.firdes.WIN_HAMMING )
self.xlate = gr.freq_xlating_fir_filter_ccc(
self.if_decim,
self.xlate_taps,
0,
self.if_rate )
self.split = gr.complex_to_float()
self.lpf = gr.fir_filter_fff(
1, self.audio_taps )
self.sum = gr.add_ff( )
self.am_sel = gr.multiply_const_ff( 0 )
self.sb_sel = gr.multiply_const_ff( 1 )
self.mixer = gr.add_ff()
self.am_det = gr.complex_to_mag()
self.connect(self, self.xlate)
self.connect(self.xlate, self.split)
self.connect((self.split, 0), (self.sum, 0))
self.connect((self.split, 1), (self.sum, 1))
self.connect(self.sum, self.sb_sel)
self.connect(self.xlate, self.am_det)
self.connect(self.sb_sel, (self.mixer, 0))
self.connect(self.am_det, self.am_sel)
self.connect(self.am_sel, (self.mixer, 1))
self.connect(self.mixer, self.lpf)
self.connect(self.lpf, self)
def upper_sb( self ):
self.xlate.set_taps([v.conjugate() for v in self.xlate_taps])
self.sb_sel.set_k( 1.0 )
self.am_sel.set_k( 0.0 )
def lower_sb( self ):
self.xlate.set_taps(self.xlate_taps)
self.sb_sel.set_k( 1.0 )
self.am_sel.set_k( 0.0 )
def set_am( self ):
taps = gr.firdes.low_pass( 1.0,
self.if_rate,
5e3,
2e3,
gr.firdes.WIN_HAMMING )
self.xlate.set_taps( taps )
self.sb_sel.set_k( 0.0 )
self.am_sel.set_k( 1.0 )
def set_bw( self, bw ):
self.audio_taps = gr.firdes.low_pass(
1.0,
self.af_rate,
bw,
600,
gr.firdes.WIN_HAMMING )
self.lpf.set_taps( self.audio_taps )
def tune( self, freq ):
self.xlate.set_center_freq( freq )
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