Imported Upstream version 3.2.2

[debian/gnuradio] / gnuradio-core / src / python / gnuradio / blks2impl / nbfm_rx.py

diff --git a/gnuradio-core/src/python/gnuradio/blks2impl/nbfm_rx.py b/gnuradio-core/src/python/gnuradio/blks2impl/nbfm_rx.py
new file mode 100644 (file)
index 0000000..dcdd460
--- /dev/null
+++ b/gnuradio-core/src/python/gnuradio/blks2impl/nbfm_rx.py
@@ -0,0 +1,88 @@
+#
+# Copyright 2005 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, optfir
+from gnuradio.blks2impl.fm_emph import fm_deemph
+#from gnuradio.blks2impl.standard_squelch import standard_squelch
+
+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].
+
+        @param audio_rate: sample rate of audio stream, >= 16k
+        @type audio_rate: integer
+        @param quad_rate: sample rate of output stream
+        @type quad_rate: integer
+        @param tau: preemphasis time constant (default 75e-6)
+        @type tau: float
+        @param max_dev: maximum deviation in Hz (default 5e3)
+        @type max_dev: 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 = gr.simple_squelch_cc(squelch_threshold, 0.001)
+
+        # FM Demodulator  input: complex; output: float
+        k = quad_rate/(2*math.pi*max_dev)
+        self.quad_demod = gr.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 = gr.firdes.low_pass (1.0,            # gain
+                                         quad_rate,      # sampling rate
+                                         2.7e3,          # Audio LPF cutoff
+                                         0.5e3,          # Transition band
+                                         gr.firdes.WIN_HAMMING)  # filter type
+
+        print "len(audio_taps) =", len(audio_taps)
+
+        # Decimating audio filter
+        # input: float; output: float; taps: float
+        self.audio_filter = gr.fir_filter_fff(audio_decim, audio_taps)
+
+        self.connect(self, self.quad_demod, self.deemph, self.audio_filter, self)