diff options
| -rwxr-xr-x | gnuradio-core/src/python/gnuradio/blks2impl/wfm_rcv_fmdet.py | 136 |
1 files changed, 81 insertions, 55 deletions
diff --git a/gnuradio-core/src/python/gnuradio/blks2impl/wfm_rcv_fmdet.py b/gnuradio-core/src/python/gnuradio/blks2impl/wfm_rcv_fmdet.py index 858b9cde6..3a93a11d6 100755 --- a/gnuradio-core/src/python/gnuradio/blks2impl/wfm_rcv_fmdet.py +++ b/gnuradio-core/src/python/gnuradio/blks2impl/wfm_rcv_fmdet.py @@ -28,8 +28,9 @@ class wfm_rcv_fmdet(gr.hier_block2): """ 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. + 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 @@ -39,16 +40,15 @@ class wfm_rcv_fmdet(gr.hier_block2): 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 + lowfreq = -125e3/demod_rate + highfreq = 125e3/demod_rate audio_rate = demod_rate / audio_decimation - - # We assign to self so that outsiders can grab the demodulator + # 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 @@ -62,25 +62,31 @@ class wfm_rcv_fmdet(gr.hier_block2): 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 + # 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) + 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 + # 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, @@ -90,101 +96,121 @@ class wfm_rcv_fmdet(gr.hier_block2): 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 + # 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) + 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_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; + 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 - 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 + # 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 + # 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) + 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 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 + # the resulting signal from this multiplier is the carrier + # with correct phase but at -38000 Hz. 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! + self.connect (self.fm_demod,self.stereo_dsbsc_filter, (self.stereo_basebander,1)) - # Pick off the real part since the imaginary is theoretically zero and then to one side of a summer + # 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 + + #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 + # 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 + + # 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 + + # 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 + + # 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 + # 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 + + # 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: |