diff options
Diffstat (limited to 'gnuradio-examples/python/usrp/limbo/am_rcv.py')
| -rwxr-xr-x | gnuradio-examples/python/usrp/limbo/am_rcv.py | 115 |
1 files changed, 115 insertions, 0 deletions
diff --git a/gnuradio-examples/python/usrp/limbo/am_rcv.py b/gnuradio-examples/python/usrp/limbo/am_rcv.py new file mode 100755 index 000000000..2908dcbf5 --- /dev/null +++ b/gnuradio-examples/python/usrp/limbo/am_rcv.py @@ -0,0 +1,115 @@ +#!/usr/bin/env python + +from gnuradio import gr, eng_notation +from gnuradio import audio +from gnuradio import usrp +from gnuradio.eng_option import eng_option +from optparse import OptionParser +import sys +import math + +from gnuradio.wxgui import stdgui, fftsink +import wx + +class am_rx_graph (stdgui.gui_flow_graph): + def __init__(self,frame,panel,vbox,argv): + stdgui.gui_flow_graph.__init__ (self,frame,panel,vbox,argv) + + station = parseargs(argv[1:]) + offset_freq = 30e3 + IF_freq = offset_freq - station + + adc_rate = 64e6 + usrp_decim = 250 + if_rate = adc_rate / usrp_decim # 256 kHz + if_decim = 4 + demod_rate = if_rate / if_decim # 64 kHz + audio_decimation = 2 + audio_rate = demod_rate / audio_decimation # 16 kHz + + # usrp is data source + src = usrp.source_c (0, usrp_decim) + src.set_rx_freq (0, IF_freq) + actual_IF_freq =src.rx_freq(0) + actual_offset = actual_IF_freq + station + + #print actual_IF_freq + #print actual_offset + + src.set_pga(0,20) + # sound card as final sink + audio_sink = audio.sink (int (audio_rate)) + + channel_coeffs = \ + gr.firdes.low_pass (1.0, # gain + if_rate, # sampling rate + 9e3, # low pass cutoff freq + 10e3, # width of trans. band + gr.firdes.WIN_HANN) + + ddc = gr.freq_xlating_fir_filter_ccf (if_decim,channel_coeffs,-actual_offset,if_rate) + + magblock = gr.complex_to_mag() + volumecontrol = gr.multiply_const_ff(.003) + + # Deemphasis. Is this necessary on AM? + TAU = 75e-6 # 75us in US, 50us in EUR + fftaps = [ 1 - math.exp(-1/TAU/if_rate), 0] + fbtaps= [ 0 , math.exp(-1/TAU/if_rate) ] + + deemph = gr.iir_filter_ffd(fftaps,fbtaps) + + # compute FIR filter taps for audio filter + width_of_transition_band = audio_rate / 8 + audio_coeffs = gr.firdes.low_pass (1.0, # gain + if_rate, # sampling rate + 9e3, #audio_rate/2 - width_of_transition_band, + 4e3, # width_of_transition_band, + gr.firdes.WIN_HANN) + + # input: float; output: float + audio_filter = gr.fir_filter_fff (audio_decimation, audio_coeffs) + + + + + print len(channel_coeffs) + print len(audio_coeffs) + + # now wire it all together + self.connect (src, ddc) + self.connect (ddc, magblock) + self.connect (magblock, volumecontrol) + self.connect (volumecontrol,deemph) + self.connect (deemph,audio_filter) + self.connect (audio_filter, (audio_sink, 0)) + + if 1: + pre_demod = fftsink.fft_sink_c (self, panel, title="Pre-Demodulation", fft_size=128, sample_rate=if_rate) + self.connect (src, pre_demod) + vbox.Add (pre_demod.win, 1, wx.EXPAND) + + if 0: + post_demod = fftsink.fft_sink_c (self, panel, title="Post Demodulation", fft_size=256, sample_rate=demod_rate) + self.connect (ddc, post_demod) + vbox.Add (post_demod.win, 1, wx.EXPAND) + + if 0: + post_filt = fftsink.fft_sink_f (self, panel, title="Post Filter", fft_size=512, sample_rate=audio_rate) + self.connect (magblock,post_filt) + vbox.Add (post_filt.win, 1, wx.EXPAND) + +def parseargs (args): + nargs = len (args) + if nargs == 1: + freq1 = float (args[0]) * 1e3 + else: + sys.stderr.write ('usage: am_rcv freq1\n') + sys.exit (1) + + return freq1 + +if __name__ == '__main__': + app = stdgui.stdapp (am_rx_graph, "AM RX") + app.MainLoop () + |