FGFS-4.1/gr-air-modes
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Everything changed.

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* Rewrote preamble detector. Uses integrate-and-dump along with correlator to perform optimal receive.
* No longer using framer. Determining packet length via header. Missing some anti-FRUIT stuff.
* Pulled out the slicer logic into its own function.

Lots of todos and fixmes.
This commit is contained in:
Nick Foster
2011-06-11 21:32:28 -07:00
parent c8dce82b75
commit 8b1c1791c7
5 changed files with 182 additions and 181 deletions
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29
src/python/uhd_modes.py
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@@ -19,9 +19,9 @@
# Boston, MA 02110-1301, USA.
#
#my_position = [37.76225, -122.44254]
my_position = [37.76225, -122.44254]
#my_position = [37.409066,-122.077836]
my_position = None
#my_position = None
from gnuradio import gr, gru, optfir, eng_notation, blks2, air
from gnuradio import uhd
@@ -92,32 +92,21 @@ class adsb_rx_block (gr.top_block):
#the DBSRX especially tends to be spur-prone; the LPF keeps out the
#spur multiple that shows up at 2MHz
# self.filtcoeffs = gr.firdes.low_pass(1, rate, 1.8e6, 200e3)
# self.filter = gr.fir_filter_fff(1, self.filtcoeffs)
#self.lpfiltcoeffs = gr.firdes.low_pass(1, rate, 1.8e6, 200e3)
#self.lpfilter = gr.fir_filter_fff(1, self.lpfiltcoeffs)
#this is an integrate-and-dump filter to act as a matched filter
#for the essentially rectangular Mode S pulses.
#if a particular Mode S transponder is using a pulse shaping filter,
#this will not be optimal.
self.filtcoeffs = list()
for i in range(int(rate/4e6)):
self.filtcoeffs.append(1.0 / (rate/4e6))
#i think downstream blocks can therefore process at 2Msps -- try this
#self.filter = gr.fir_filter_fff(int(rate/2e6), self.filtcoeffs)
self.filter = gr.fir_filter_fff(1, self.filtcoeffs)
#rate = int(2e6)
self.preamble = air.modes_preamble(rate, options.threshold)
self.framer = air.modes_framer(rate)
#self.framer = air.modes_framer(rate)
self.slicer = air.modes_slicer(rate, queue)
self.connect(self.u, self.demod, self.filter)
self.connect(self.filter, self.avg)
self.connect(self.filter, (self.preamble, 0))
self.connect(self.u, self.demod)
self.connect(self.demod, self.avg)
self.connect(self.demod, (self.preamble, 0))
self.connect(self.avg, (self.preamble, 1))
self.connect((self.preamble, 0), (self.framer, 0))
self.connect(self.framer, self.slicer)
self.connect((self.preamble, 0), (self.slicer, 0))
def tune(self, freq):
result = self.u.set_center_freq(freq, 0)