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# This tries to push the hilbert transform for ssb demod back into the
# freq. xlating filter.
#
# The usual gnuradio copyright notice is hereby included by reference.
#
# 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, gru
from gnuradio import audio
from gnuradio import usrp
class ssb_demod( gr.hier_block ):
def __init__( self, fg, if_rate, af_rate ):
self.if_rate = if_rate
self.af_rate = af_rate
self.if_decim = 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()
fg.connect( self.xlate, self.split )
fg.connect( ( self.split,0 ), ( self.sum,0 ) )
fg.connect( ( self.split,1 ), ( self.sum,1 ) )
fg.connect( self.sum, self.sb_sel )
fg.connect( self.xlate, self.am_det )
fg.connect( self.sb_sel, ( self.mixer, 0 ) )
fg.connect( self.am_det, self.am_sel )
fg.connect( self.am_sel, ( self.mixer, 1 ) )
fg.connect( self.mixer, self.lpf )
gr.hier_block.__init__( self, fg, self.xlate, self.lpf )
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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