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# post detection agc processing
#
# Imagine that the usual gnuradio copyright stuff is right here.
#
# This agc strategy is copied more or less verbatim from
# weaver_isb_am1_usrp3.py by cswiger.
#
# Thanks.
#
# Then modified in a variety of ways.
#
# There doesn't appear to be a way to hook multiple blocks to the
# input port when building a hier block like this. Thus the
# split below.
#
# Basic operation.
# Power is estimated by squaring the input.
# Low pass filter using a 1 pole iir.
# The time constant can be tweaked by changing the taps.
# Currently there is no implementation to change this while operating
# a potentially useful addition.
# The log block turns this into dB
# gain adjusts the agc authority.
#
# M. Revnell 2006-Jan
from gnuradio import gr, gru
class agc( gr.hier_block ):
def __init__( self, fg ):
self.split = gr.multiply_const_ff( 1 )
self.sqr = gr.multiply_ff( )
self.int0 = gr.iir_filter_ffd( [.004, 0], [0, .999] )
self.offs = gr.add_const_ff( -30 )
self.gain = gr.multiply_const_ff( 70 )
self.log = gr.nlog10_ff( 10, 1 )
self.agc = gr.divide_ff( )
fg.connect( self.split, ( self.agc, 0 ) )
fg.connect( self.split, ( self.sqr, 0 ) )
fg.connect( self.split, ( self.sqr, 1 ) )
fg.connect( self.sqr, self.int0 )
fg.connect( self.int0, self.log )
fg.connect( self.log, self.offs )
fg.connect( self.offs, self.gain )
fg.connect( self.gain, ( self.agc, 1 ) )
gr.hier_block.__init__( self, fg, self.split, self.agc )
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