1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
|
#
# Copyright 2005,2007,2012 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.
#
import math
from gnuradio import gr
from gnuradio import filter
from fm_emph import fm_preemph
try:
from gnuradio import analog
except ImportError:
import analog_swig as analog
class wfm_tx(gr.hier_block2):
def __init__(self, audio_rate, quad_rate, tau=75e-6, max_dev=75e3):
"""
Wide Band FM Transmitter.
Takes a single float input stream of audio samples in the range [-1,+1]
and produces a single FM modulated complex baseband output.
Args:
audio_rate: sample rate of audio stream, >= 16k (integer)
quad_rate: sample rate of output stream (integer)
tau: preemphasis time constant (default 75e-6) (float)
max_dev: maximum deviation in Hz (default 75e3) (float)
quad_rate must be an integer multiple of audio_rate.
"""
gr.hier_block2.__init__(self, "wfm_tx",
gr.io_signature(1, 1, gr.sizeof_float), # Input signature
gr.io_signature(1, 1, gr.sizeof_gr_complex)) # Output signature
# FIXME audio_rate and quad_rate ought to be exact rationals
audio_rate = int(audio_rate)
quad_rate = int(quad_rate)
if quad_rate % audio_rate != 0:
raise ValueError, "quad_rate is not an integer multiple of audio_rate"
do_interp = audio_rate != quad_rate
if do_interp:
interp_factor = quad_rate / audio_rate
interp_taps = filter.optfir.low_pass(interp_factor, # gain
quad_rate, # Fs
16000, # passband cutoff
18000, # stopband cutoff
0.1, # passband ripple dB
40) # stopband atten dB
print "len(interp_taps) =", len(interp_taps)
self.interpolator = filter.interp_fir_filter_fff (interp_factor, interp_taps)
self.preemph = fm_preemph(quad_rate, tau=tau)
k = 2 * math.pi * max_dev / quad_rate
self.modulator = analog.frequency_modulator_fc (k)
if do_interp:
self.connect(self, self.interpolator, self.preemph, self.modulator, self)
else:
self.connect(self, self.preemph, self.modulator, self)
|
