2 # Copyright 2005 Free Software Foundation, Inc.
4 # This file is part of GNU Radio
6 # GNU Radio is free software; you can redistribute it and/or modify
7 # it under the terms of the GNU General Public License as published by
8 # the Free Software Foundation; either version 2, or (at your option)
11 # GNU Radio is distributed in the hope that it will be useful,
12 # but WITHOUT ANY WARRANTY; without even the implied warranty of
13 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 # GNU General Public License for more details.
16 # You should have received a copy of the GNU General Public License
17 # along with GNU Radio; see the file COPYING. If not, write to
18 # the Free Software Foundation, Inc., 51 Franklin Street,
19 # Boston, MA 02110-1301, USA.
23 from gnuradio import gr, optfir
24 from gnuradio.blksimpl.fm_emph import fm_preemph
26 class wfm_tx(gr.hier_block):
27 def __init__(self, fg, audio_rate, quad_rate, tau=75e-6, max_dev=75e3):
29 Wide Band FM Transmitter.
31 Takes a single float input stream of audio samples in the range [-1,+1]
32 and produces a single FM modulated complex baseband output.
35 @param audio_rate: sample rate of audio stream, >= 16k
36 @type audio_rate: integer
37 @param quad_rate: sample rate of output stream
38 @type quad_rate: integer
39 @param tau: preemphasis time constant (default 75e-6)
41 @param max_dev: maximum deviation in Hz (default 75e3)
44 quad_rate must be an integer multiple of audio_rate.
47 # FIXME audio_rate and quad_rate ought to be exact rationals
48 audio_rate = int(audio_rate)
49 quad_rate = int(quad_rate)
51 if quad_rate % audio_rate != 0:
52 raise ValueError, "quad_rate is not an integer multiple of audio_rate"
55 do_interp = audio_rate != quad_rate
58 interp_factor = quad_rate / audio_rate
59 interp_taps = optfir.low_pass (interp_factor, # gain
61 16000, # passband cutoff
62 18000, # stopband cutoff
63 0.1, # passband ripple dB
64 40) # stopband atten dB
66 print "len(interp_taps) =", len(interp_taps)
67 self.interpolator = gr.interp_fir_filter_fff (interp_factor, interp_taps)
69 self.preemph = fm_preemph (fg, quad_rate, tau=tau)
71 k = 2 * math.pi * max_dev / quad_rate
72 self.modulator = gr.frequency_modulator_fc (k)
75 fg.connect (self.interpolator, self.preemph, self.modulator)
76 gr.hier_block.__init__(self, fg, self.interpolator, self.modulator)
78 fg.connect(self.preemph, self.modulator)
79 gr.hier_block.__init__(self, fg, self.preemph, self.modulator)