updates to c4fm pre-emphasis and de-emphasis filtering
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@ -2,7 +2,7 @@
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# Copyright 2005,2006,2007 Free Software Foundation, Inc.
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#
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# OP25 Demodulator Block
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# Copyright 2009, 2010, 2011, 2012, 2013, 2014 Max H. Parke KA1RBI
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# Copyright 2009, 2010, 2011, 2012, 2013, 2014, 2015 Max H. Parke KA1RBI
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#
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# This file is part of GNU Radio and part of OP25
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#
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@ -26,6 +26,7 @@
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P25 C4FM/CQPSK demodulation block.
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"""
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import sys
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from gnuradio import gr, gru, eng_notation
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from gnuradio import filter, analog, digital, blocks
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from gnuradio.eng_option import eng_option
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@ -33,9 +34,11 @@ import op25
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import op25_repeater
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from math import pi
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sys.path.append('tx')
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import op25_c4fm_mod
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# default values (used in __init__ and add_options)
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_def_output_sample_rate = 48000
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_def_excess_bw = 0.1
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_def_if_rate = 24000
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_def_gain_mu = 0.025
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_def_costas_alpha = 0.04
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@ -62,11 +65,8 @@ class p25_demod_base(gr.hier_block2):
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self.bb_sink = None
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self.baseband_amp = blocks.multiply_const_ff(_def_bb_gain)
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sps = int(self.if_rate // self.symbol_rate)
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symbol_decim = 1
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ntaps = 11 * sps
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rrc_coeffs = (1.0/sps,)*sps
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self.symbol_filter = filter.fir_filter_fff(symbol_decim, rrc_coeffs)
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coeffs = op25_c4fm_mod.c4fm_taps(sample_rate=self.if_rate, span=9, generator=op25_c4fm_mod.transfer_function_rx).generate()
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self.symbol_filter = filter.fir_filter_fff(1, coeffs)
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autotuneq = gr.msg_queue(2)
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self.fsk4_demod = op25.fsk4_demod_ff(autotuneq, self.if_rate, self.symbol_rate)
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@ -168,7 +168,7 @@ class p25_demod_cb(p25_demod_base):
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# local osc
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self.lo = analog.sig_source_c (input_rate, analog.GR_SIN_WAVE, 0, 1.0, 0)
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self.mixer = blocks.multiply_cc()
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lpf_coeffs = filter.firdes.low_pass(1.0, input_rate, 15000, 1500, filter.firdes.WIN_HANN)
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lpf_coeffs = filter.firdes.low_pass(1.0, input_rate, 7250, 725, filter.firdes.WIN_HANN)
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decimation = int(input_rate / if_rate)
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self.lpf = filter.fir_filter_ccf(decimation, lpf_coeffs)
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@ -2,7 +2,7 @@
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# Copyright 2008-2011 Steve Glass
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#
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# Copyright 2011, 2012, 2013, 2014 Max H. Parke KA1RBI
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# Copyright 2011, 2012, 2013, 2014, 2015 Max H. Parke KA1RBI
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#
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# Copyright 2003,2004,2005,2006 Free Software Foundation, Inc.
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# (from radiorausch)
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@ -418,6 +418,7 @@ class p25_rx_block (stdgui2.std_top_block):
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sel = self.notebook.GetSelection()
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self.lock()
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self.disconnect_data_scope()
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if not self.baseband_input:
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self.disconnect_constellation_scope()
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if sel == 0: # spectrum
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if not self.baseband_input:
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@ -871,7 +872,7 @@ class p25_rx_block (stdgui2.std_top_block):
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self.state = new_state
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if "STOPPED" == self.state:
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# menu items
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can_capture = self.usrp is not None
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can_capture = False # self.usrp is not None
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self.file_new.Enable(can_capture)
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self.file_open.Enable(True)
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self.file_properties.Enable(False)
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@ -2,9 +2,7 @@
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# Copyright 2005,2006,2007 Free Software Foundation, Inc.
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#
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# OP25 4-Level Modulator Block
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# Copyright 2009, 2014 Max H. Parke KA1RBI
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#
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# coeffs for shaping and cosine filters from Eric Ramsey thesis
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# Copyright 2009, 2010, 2011, 2012, 2013, 2014, 2015 Max H. Parke KA1RBI
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#
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# This file is part of GNU Radio and part of OP25
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#
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@ -34,13 +32,69 @@ from gnuradio import filter, digital, blocks
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from gnuradio.eng_option import eng_option
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from optparse import OptionParser
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import math
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from math import sin, cos, pi
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import numpy as np
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# default values (used in __init__ and add_options)
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_def_output_sample_rate = 48000
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_def_excess_bw = 0.2
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_def_symbol_rate = 4800
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_def_reverse = False
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_def_verbose = False
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_def_log = False
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_def_span = 13 #desired number of impulse response coeffs, in units of symbols
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def transfer_function_rx():
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# p25 c4fm de-emphasis filter
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# Specs undefined above 2,880 Hz. It would be nice to have a sharper
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# rolloff, but this filter is cheap enough....
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xfer = [] # frequency domain transfer function
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for f in xrange(0,4800):
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# D(f)
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t = pi * f / 4800
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if t < 1e-6:
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df = 1.0
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else:
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df = sin (t) / t
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xfer.append(df)
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return xfer
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def transfer_function_tx():
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xfer = [] # frequency domain transfer function
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for f in xrange(0, 2881): # specs cover 0 - 2,880 Hz
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# H(f)
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if f < 1920:
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hf = 1.0
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else:
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hf = 0.5 + 0.5 * cos (2 * pi * float(f) / 1920.0)
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# P(f)
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t = pi * f / 4800.0
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if t < 1e-6:
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pf = 1
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else:
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pf = t / sin (t)
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# time domain convolution == frequency domain multiplication
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xfer.append(pf * hf)
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return xfer
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class c4fm_taps(object):
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"""Generate filter coefficients as per P25 C4FM spec"""
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def __init__(self, filter_gain = 1.0, sample_rate=_def_output_sample_rate, symbol_rate=_def_symbol_rate, span=_def_span, generator=transfer_function_tx):
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self.sample_rate = sample_rate
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self.symbol_rate = symbol_rate
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self.filter_gain = filter_gain
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self.sps = int(sample_rate / symbol_rate)
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self.ntaps = (self.sps * span) | 1
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self.generator = generator
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def generate(self):
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impulse_response = np.fft.fftshift(np.fft.irfft(self.generator(), self.sample_rate))
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start = np.argmax(impulse_response) - (self.ntaps-1) / 2
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coeffs = impulse_response[start: start+self.ntaps]
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gain = self.filter_gain / sum(coeffs)
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return coeffs * gain
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def generate_code(self, varname='taps'):
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return '%s = [\n\t%s]' % (varname, ',\n\t'.join(['%10.6e' % f for f in self.generate()]))
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# /////////////////////////////////////////////////////////////////////////////
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# modulator
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@ -50,7 +104,6 @@ class p25_mod_bf(gr.hier_block2):
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def __init__(self,
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output_sample_rate=_def_output_sample_rate,
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excess_bw=_def_excess_bw,
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reverse=_def_reverse,
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verbose=_def_verbose,
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log=_def_log):
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@ -66,8 +119,6 @@ class p25_mod_bf(gr.hier_block2):
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@param output_sample_rate: output sample rate
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@type output_sample_rate: integer
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@param excess_bw: Root-raised cosine filter excess bandwidth
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@type excess_bw: float
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@param reverse: reverse polarity flag
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@type reverse: bool
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@param verbose: Print information about modulator?
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@ -84,7 +135,6 @@ class p25_mod_bf(gr.hier_block2):
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lcm = gru.lcm(input_sample_rate, output_sample_rate)
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self._interp_factor = int(lcm // input_sample_rate)
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self._decimation = int(lcm // output_sample_rate)
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self._excess_bw = excess_bw
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mod_map = [1.0/3.0, 1.0, -(1.0/3.0), -1.0]
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self.C2S = digital.chunks_to_symbols_bf(mod_map)
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@ -93,27 +143,7 @@ class p25_mod_bf(gr.hier_block2):
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else:
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self.polarity = blocks.multiply_const_ff( 1)
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ntaps = 11 * self._interp_factor
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rrc_taps = filter.firdes.root_raised_cosine(
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self._interp_factor, # gain (since we're interpolating by sps)
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lcm, # sampling rate
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input_sample_rate, # symbol rate
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self._excess_bw, # excess bandwidth (roll-off factor)
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ntaps)
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# rrc_coeffs work slightly differently: each input sample
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# (from mod_map above) at 4800 rate, then 9 zeros are inserted
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# to bring to 48000 rate, then this filter is applied:
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# rrc_filter = gr.fir_filter_fff(1, rrc_coeffs)
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# FIXME: how to insert the 9 zero samples using gr ?
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# rrc_coeffs = [0, -0.003, -0.006, -0.009, -0.012, -0.014, -0.014, -0.013, -0.01, -0.006, 0, 0.007, 0.014, 0.02, 0.026, 0.029, 0.029, 0.027, 0.021, 0.012, 0, -0.013, -0.027, -0.039, -0.049, -0.054, -0.055, -0.049, -0.038, -0.021, 0, 0.024, 0.048, 0.071, 0.088, 0.098, 0.099, 0.09, 0.07, 0.039, 0, -0.045, -0.091, -0.134, -0.17, -0.193, -0.199, -0.184, -0.147, -0.085, 0, 0.105, 0.227, 0.36, 0.496, 0.629, 0.751, 0.854, 0.933, 0.983, 1, 0.983, 0.933, 0.854, 0.751, 0.629, 0.496, 0.36, 0.227, 0.105, 0, -0.085, -0.147, -0.184, -0.199, -0.193, -0.17, -0.134, -0.091, -0.045, 0, 0.039, 0.07, 0.09, 0.099, 0.098, 0.088, 0.071, 0.048, 0.024, 0, -0.021, -0.038, -0.049, -0.055, -0.054, -0.049, -0.039, -0.027, -0.013, 0, 0.012, 0.021, 0.027, 0.029, 0.029, 0.026, 0.02, 0.014, 0.007, 0, -0.006, -0.01, -0.013, -0.014, -0.014, -0.012, -0.009, -0.006, -0.003, 0]
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self.rrc_filter = filter.interp_fir_filter_fff(self._interp_factor, rrc_taps)
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# FM pre-emphasis filter
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shaping_coeffs = [-0.018, 0.0347, 0.0164, -0.0064, -0.0344, -0.0522, -0.0398, 0.0099, 0.0798, 0.1311, 0.121, 0.0322, -0.113, -0.2499, -0.3007, -0.2137, -0.0043, 0.2825, 0.514, 0.604, 0.514, 0.2825, -0.0043, -0.2137, -0.3007, -0.2499, -0.113, 0.0322, 0.121, 0.1311, 0.0798, 0.0099, -0.0398, -0.0522, -0.0344, -0.0064, 0.0164, 0.0347, -0.018]
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self.shaping_filter = filter.fir_filter_fff(1, shaping_coeffs)
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self.filter = filter.interp_fir_filter_fff(self._interp_factor, c4fm_taps(sample_rate=output_sample_rate).generate())
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if verbose:
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self._print_verbage()
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@ -121,16 +151,15 @@ class p25_mod_bf(gr.hier_block2):
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if log:
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self._setup_logging()
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self.connect(self, self.C2S, self.polarity, self.rrc_filter, self.shaping_filter)
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self.connect(self, self.C2S, self.polarity, self.filter)
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if (self._decimation > 1):
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self.decimator = filter.rational_resampler_fff(1, self._decimation)
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self.connect(self.shaping_filter, self.decimator, self)
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self.connect(self.filter, self.decimator, self)
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else:
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self.connect(self.shaping_filter, self)
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self.connect(self.filter, self)
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def _print_verbage(self):
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print "\nModulator:"
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print "RRS roll-off factor: %f" % self._excess_bw
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print "interpolation: %d decimation: %d" %(self._interp_factor, self._decimation)
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def _setup_logging(self):
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@ -139,8 +168,8 @@ class p25_mod_bf(gr.hier_block2):
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gr.file_sink(gr.sizeof_float, "tx_chunks2symbols.dat"))
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self.connect(self.polarity,
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gr.file_sink(gr.sizeof_float, "tx_polarity.dat"))
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self.connect(self.rrc_filter,
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gr.file_sink(gr.sizeof_float, "tx_rrc_filter.dat"))
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self.connect(self.filter,
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gr.file_sink(gr.sizeof_float, "tx_filter.dat"))
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self.connect(self.shaping_filter,
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gr.file_sink(gr.sizeof_float, "tx_shaping_filter.dat"))
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if (self._decimation > 1):
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@ -151,8 +180,6 @@ class p25_mod_bf(gr.hier_block2):
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"""
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Adds QPSK modulation-specific options to the standard parser
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"""
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parser.add_option("", "--excess-bw", type="float", default=_def_excess_bw,
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help="set RRC excess bandwith factor [default=%default] (PSK)")
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add_options=staticmethod(add_options)
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