From ae30f247616b6229fb304e30fecf3f82ae09dbf6 Mon Sep 17 00:00:00 2001 From: Ben Reynwar <ben@reynwar.net> Date: Thu, 7 Mar 2013 23:27:44 -0700 Subject: analog: Enabling uninstalled python imports. --- gr-analog/python/analog/nbfm_rx.py | 90 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 90 insertions(+) create mode 100644 gr-analog/python/analog/nbfm_rx.py (limited to 'gr-analog/python/analog/nbfm_rx.py') diff --git a/gr-analog/python/analog/nbfm_rx.py b/gr-analog/python/analog/nbfm_rx.py new file mode 100644 index 0000000000..b2c86db70f --- /dev/null +++ b/gr-analog/python/analog/nbfm_rx.py @@ -0,0 +1,90 @@ +# +# Copyright 2005,2012 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_deemph + +try: + from gnuradio import analog +except ImportError: + import analog_swig as analog + +class nbfm_rx(gr.hier_block2): + def __init__(self, audio_rate, quad_rate, tau=75e-6, max_dev=5e3): + """ + Narrow Band FM Receiver. + + Takes a single complex baseband input stream and produces a single + float output stream of audio sample in the range [-1, +1]. + + 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) + + quad_rate must be an integer multiple of audio_rate. + + Exported sub-blocks (attributes): + squelch + quad_demod + deemph + audio_filter + """ + + gr.hier_block2.__init__(self, "nbfm_rx", + gr.io_signature(1, 1, gr.sizeof_gr_complex), # Input signature + gr.io_signature(1, 1, gr.sizeof_float)) # 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" + + squelch_threshold = 20 # dB + #self.squelch = analog.simple_squelch_cc(squelch_threshold, 0.001) + + # FM Demodulator input: complex; output: float + k = quad_rate/(2*math.pi*max_dev) + self.quad_demod = analog.quadrature_demod_cf(k) + + # FM Deemphasis IIR filter + self.deemph = fm_deemph(quad_rate, tau=tau) + + # compute FIR taps for audio filter + audio_decim = quad_rate // audio_rate + audio_taps = filter.firdes.low_pass(1.0, # gain + quad_rate, # sampling rate + 2.7e3, # Audio LPF cutoff + 0.5e3, # Transition band + filter.firdes.WIN_HAMMING) # filter type + + print "len(audio_taps) =", len(audio_taps) + + # Decimating audio filter + # input: float; output: float; taps: float + self.audio_filter = filter.fir_filter_fff(audio_decim, audio_taps) + + self.connect(self, self.quad_demod, self.deemph, self.audio_filter, self) -- cgit v1.2.3