new fm detector added based on FIR derivative detector. Stereo sep better than pll based one and more efficient. Tweaking probably needed, usrp_wfm_rcv_fmdet added to demo

git-svn-id: http://gnuradio.org/svn/gnuradio/trunk@10847 221aa14e-8319-0410-a670-987f0aec2ac5

2 files changed, 192 insertions, 0 deletions

diff --git a/gnuradio-core/src/python/gnuradio/blks2impl/Makefile.am b/gnuradio-core/src/python/gnuradio/blks2impl/Makefile.am
index 09cd92fc3..f07abd4c4 100644
--- a/gnuradio-core/src/python/gnuradio/blks2impl/Makefile.am
+++ b/gnuradio-core/src/python/gnuradio/blks2impl/Makefile.am
@@ -58,5 +58,6 @@ grblkspython_PYTHON =		\
 	standard_squelch.py	\
 	stream_to_vector_decimator.py \
 	wfm_rcv.py		\
+	wfm_rcv_fmdet.py	\
 	wfm_rcv_pll.py		\
 	wfm_tx.py		
diff --git a/gnuradio-core/src/python/gnuradio/blks2impl/wfm_rcv_fmdet.py b/gnuradio-core/src/python/gnuradio/blks2impl/wfm_rcv_fmdet.py
new file mode 100755
index 000000000..858b9cde6
--- /dev/null
+++ b/gnuradio-core/src/python/gnuradio/blks2impl/wfm_rcv_fmdet.py
@@ -0,0 +1,191 @@
+#
+# Copyright 2005,2006 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.
+# 
+
+from gnuradio import gr
+from gnuradio.blks2impl.fm_emph import fm_deemph
+import math
+
+class wfm_rcv_fmdet(gr.hier_block2):
+    def __init__ (self, demod_rate, audio_decimation):
+        """
+        Hierarchical block for demodulating a broadcast FM signal.
+        
+        The input is the downconverted complex baseband signal (gr_complex).
+        The output is two streams of the demodulated audio (float) 0=Left, 1=Right.
+        
+        @param demod_rate: input sample rate of complex baseband input.
+        @type demod_rate: float
+        @param audio_decimation: how much to decimate demod_rate to get to audio.
+        @type audio_decimation: integer
+        """
+	gr.hier_block2.__init__(self, "wfm_rcv_fmdet",
+				gr.io_signature(1, 1, gr.sizeof_gr_complex), # Input signature
+				gr.io_signature(2, 2, gr.sizeof_float))      # Output signature
+        lowfreq = -125e3
+	highfreq = 125e3
+        audio_rate = demod_rate / audio_decimation
+
+
+        # We assign to self so that outsiders can grab the demodulator 
+        # if they need to.  E.g., to plot its output.
+        #
+        # input: complex; output: float
+            
+        self.fm_demod = gr.fmdet_cf (demod_rate, lowfreq, highfreq, 0.05)
+
+        # input: float; output: float
+        self.deemph_Left  = fm_deemph (audio_rate)
+        self.deemph_Right = fm_deemph (audio_rate)
+        
+        # compute FIR filter taps for audio filter
+        width_of_transition_band = audio_rate / 32
+        audio_coeffs = gr.firdes.low_pass (1.0 ,         # gain
+                                           demod_rate,      # sampling rate
+                                           15000 ,
+                                           width_of_transition_band,
+                                           gr.firdes.WIN_HAMMING)
+        # input: float; output: float
+        self.audio_filter = gr.fir_filter_fff (audio_decimation, audio_coeffs)
+        if 1:
+            # Pick off the stereo carrier/2 with this filter. It attenuated 10 dB so apply 10 dB gain
+            # We pick off the negative frequency half because we want to base band by it!
+            ##  NOTE  THIS WAS HACKED TO OFFSET INSERTION LOSS DUE TO DEEMPHASIS
+
+            stereo_carrier_filter_coeffs = gr.firdes.complex_band_pass(10.0,
+                                                                   demod_rate,
+                                                                   -19020,
+                                                                   -18980,
+                                                                   width_of_transition_band,
+                                                                   gr.firdes.WIN_HAMMING)
+            
+            #print "len stereo carrier filter = ",len(stereo_carrier_filter_coeffs)
+            #print "stereo carrier filter ", stereo_carrier_filter_coeffs
+            #print "width of transition band = ",width_of_transition_band, " audio rate = ", audio_rate
+
+            # Pick off the double side band suppressed carrier Left-Right audio. It is attenuated 10 dB so apply 10 dB gain
+
+            stereo_dsbsc_filter_coeffs = gr.firdes.complex_band_pass(20.0,
+                                                                     demod_rate,
+                                                                     38000-15000/2,
+                                                                     38000+15000/2,
+                                                                     width_of_transition_band,
+                                                                     gr.firdes.WIN_HAMMING)
+            #print "len stereo dsbsc filter = ",len(stereo_dsbsc_filter_coeffs)
+            #print "stereo dsbsc filter ", stereo_dsbsc_filter_coeffs
+            # construct overlap add filter system from coefficients for stereo carrier
+
+            self.stereo_carrier_filter = gr.fir_filter_fcc(audio_decimation, stereo_carrier_filter_coeffs)
+
+            # carrier is twice the picked off carrier so arrange to do a commplex multiply
+
+            self.stereo_carrier_generator = gr.multiply_cc();
+
+            # Pick off the rds signal
+
+            stereo_rds_filter_coeffs = gr.firdes.complex_band_pass(30.0,
+                                                                     demod_rate,
+                                                                     57000 - 1500,
+                                                                     57000 + 1500,
+                                                                     width_of_transition_band,
+                                                                     gr.firdes.WIN_HAMMING)
+            #print "len stereo dsbsc filter = ",len(stereo_dsbsc_filter_coeffs)
+            #print "stereo dsbsc filter ", stereo_dsbsc_filter_coeffs
+            # construct overlap add filter system from coefficients for stereo carrier
+
+	    self.rds_signal_filter = gr.fir_filter_fcc(audio_decimation, stereo_rds_filter_coeffs)
+
+
+
+
+
+
+	    self.rds_carrier_generator = gr.multiply_cc();
+	    self.rds_signal_generator = gr.multiply_cc();
+	    self_rds_signal_processor = gr.null_sink(gr.sizeof_gr_complex);
+
+
+
+            alpha = 5 * 0.25 * math.pi / (audio_rate)
+            beta = alpha * alpha / 4.0
+            max_freq = -2.0*math.pi*18990/audio_rate;
+            min_freq = -2.0*math.pi*19010/audio_rate;
+            
+            self.stereo_carrier_pll_recovery = gr.pll_refout_cc(alpha,beta,max_freq,min_freq);
+            #self.stereo_carrier_pll_recovery.squelch_enable(False) #pll_refout does not have squelch yet, so disabled for now 
+            
+
+            # set up mixer (multiplier) to get the L-R signal at baseband
+
+            self.stereo_basebander = gr.multiply_cc();
+
+            # pick off the real component of the basebanded L-R signal.  The imaginary SHOULD be zero
+
+            self.LmR_real = gr.complex_to_real();
+            self.Make_Left = gr.add_ff();
+            self.Make_Right = gr.sub_ff();
+            
+            self.stereo_dsbsc_filter = gr.fir_filter_fcc(audio_decimation, stereo_dsbsc_filter_coeffs)
+
+
+        if 1:
+
+            # send the real signal to complex filter to pick off the carrier and then to one side of a multiplier
+            self.connect (self, self.fm_demod,self.stereo_carrier_filter,self.stereo_carrier_pll_recovery, (self.stereo_carrier_generator,0))
+            # send the already filtered carrier to the otherside of the carrier
+            self.connect (self.stereo_carrier_pll_recovery, (self.stereo_carrier_generator,1))
+            # the resulting signal from this multiplier is the carrier with correct phase but at -38000 Hz.
+
+            # send the new carrier to one side of the mixer (multiplier)
+            self.connect (self.stereo_carrier_generator, (self.stereo_basebander,0))
+            # send the demphasized audio to the DSBSC pick off filter,  the complex
+            # DSBSC signal at +38000 Hz is sent to the other side of the mixer/multiplier
+            self.connect (self.fm_demod,self.stereo_dsbsc_filter, (self.stereo_basebander,1))
+            # the result is BASEBANDED DSBSC with phase zero!
+
+            # Pick off the real part since the imaginary is theoretically zero and then to one side of a summer
+            self.connect (self.stereo_basebander, self.LmR_real, (self.Make_Left,0))
+            #take the same real part of the DSBSC baseband signal and send it to negative side of a subtracter
+            self.connect (self.LmR_real,(self.Make_Right,1))
+
+	    # Make rds carrier by taking the squared pilot tone and multiplying by pilot tone
+	    self.connect (self.stereo_basebander,(self.rds_carrier_generator,0))
+            self.connect (self.stereo_carrier_pll_recovery,(self.rds_carrier_generator,1)) 
+	    # take signal, filter off rds,  send into mixer 0 channel
+	    self.connect (self.fm_demod,self.rds_signal_filter,(self.rds_signal_generator,0))
+            # take rds_carrier_generator output and send into mixer 1 channel
+	    self.connect (self.rds_carrier_generator,(self.rds_signal_generator,1))
+	    # send basebanded rds signal and send into "processor" which for now is a null sink
+	    self.connect (self.rds_signal_generator,self_rds_signal_processor)
+	    
+
+        if 1:
+            # pick off the audio, L+R that is what we used to have and send it to the summer
+            self.connect(self.fm_demod, self.audio_filter, (self.Make_Left, 1))
+            # take the picked off L+R audio and send it to the PLUS side of the subtractor
+            self.connect(self.audio_filter,(self.Make_Right, 0))
+            # The result of  Make_Left  gets    (L+R) +  (L-R) and results in 2*L
+            # The result of Make_Right gets  (L+R) - (L-R) and results in 2*R
+            self.connect(self.Make_Left , self.deemph_Left, (self, 0))
+            self.connect(self.Make_Right, self.deemph_Right, (self, 1))
+        # NOTE: mono support will require variable number of outputs in hier_block2s
+        # See ticket:174 in Trac database
+        #else:
+        #    self.connect (self.fm_demod, self.audio_filter, self)