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#
# Copyright 2005,2012 Free Software Foundation, Inc.
#
# This file is part of GNU Radio
#
# SPDX-License-Identifier: GPL-3.0-or-later
#
#
import math
from gnuradio import gr, filter
from .fm_emph import fm_preemph
from . import analog_python as analog
class nbfm_tx(gr.hier_block2):
"""
Narrow 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 5e3) (float)
fh: high frequency at which to flatten preemphasis; < 0 means default of 0.925*quad_rate/2.0 (float)
quad_rate must be an integer multiple of audio_rate.
"""
def __init__(self, audio_rate, quad_rate, tau=75e-6, max_dev=5e3, fh=-1.0):
gr.hier_block2.__init__(self, "nbfm_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
self._audio_rate = audio_rate = int(audio_rate)
self._quad_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 = int(quad_rate / audio_rate) # force integer
interp_taps = filter.optfir.low_pass(interp_factor, # gain
quad_rate, # Fs
4500, # passband cutoff
7000, # 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, fh=fh)
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)
def set_max_deviation(self, max_dev):
k = 2 * math.pi * max_dev / self._quad_rate
self.modulator.set_sensitivity(k)
class ctcss_gen_f(gr.hier_block2):
def __init__(self, sample_rate, tone_freq):
gr.hier_block2.__init__(self, "ctcss_gen_f",
gr.io_signature(0, 0, 0), # Input signature
gr.io_signature(1, 1, gr.sizeof_float)) # Output signature
self.plgen = analog.sig_source_f(sample_rate, analog.GR_SIN_WAVE,
tone_freq, 0.1, 0.0)
self.connect(self.plgen, self)
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