2 # Copyright 2005,2007 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 3, 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.blks2impl.fm_emph import fm_preemph
26 class wfm_tx(gr.hier_block2):
27 def __init__(self, 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.
34 @param audio_rate: sample rate of audio stream, >= 16k
35 @type audio_rate: integer
36 @param quad_rate: sample rate of output stream
37 @type quad_rate: integer
38 @param tau: preemphasis time constant (default 75e-6)
40 @param max_dev: maximum deviation in Hz (default 75e3)
43 quad_rate must be an integer multiple of audio_rate.
45 gr.hier_block2.__init__(self, "wfm_tx",
46 gr.io_signature(1, 1, gr.sizeof_float), # Input signature
47 gr.io_signature(1, 1, gr.sizeof_gr_complex)) # Output signature
49 # FIXME audio_rate and quad_rate ought to be exact rationals
50 audio_rate = int(audio_rate)
51 quad_rate = int(quad_rate)
53 if quad_rate % audio_rate != 0:
54 raise ValueError, "quad_rate is not an integer multiple of audio_rate"
57 do_interp = audio_rate != quad_rate
60 interp_factor = quad_rate / audio_rate
61 interp_taps = optfir.low_pass (interp_factor, # gain
63 16000, # passband cutoff
64 18000, # stopband cutoff
65 0.1, # passband ripple dB
66 40) # stopband atten dB
68 print "len(interp_taps) =", len(interp_taps)
69 self.interpolator = gr.interp_fir_filter_fff (interp_factor, interp_taps)
71 self.preemph = fm_preemph (quad_rate, tau=tau)
73 k = 2 * math.pi * max_dev / quad_rate
74 self.modulator = gr.frequency_modulator_fc (k)
77 self.connect (self, self.interpolator, self.preemph, self.modulator, self)
79 self.connect(self, self.preemph, self.modulator, self)