Hi all,
This was the bug mentioned in December by Mr. Martin and
now iam having the same problem. Iam trying to demodulate a QPSK
signal and during the carrier recovery process, iam trying to multiply
the filtered, squared signal with the signal but it is not giving any
ouput. The output blinks on the scope for a second and then remains
calm. Is this really buffer allocation problem, if it so then may I
know if it is fixed or not. Thank you all for suggestions. Iam
attaching a small test program that illustrates this problem.
Rana.
#............. Program to illustrate the bug ....................#
from gnuradio import gr
from gnuradio import audio
import sys
import math
def build_graph ():
fg = gr.flow_graph ()
samps_per_symbol = 32
samp_freq =16000
carrier_freq = 1900
src = gr.file_source(gr.sizeof_float, "qpsk_input_num")
dst = audio.sink (samp_freq)
#............... Band Pass FIltering at the front end of the reciever
................... #
audio_coeffs1 = gr.firdes.band_pass (
1.0, # gain
samp_freq,
1400, # center of low transition band
2400, # center of hi transition band
600, # width of transition band
gr.firdes.WIN_HAMMING)
audio_filter1 = gr.fir_filter_fff ( 1, audio_coeffs1)
i_demod_mixer = gr.multiply_ff()
fg.connect(src,audio_filter1)
fg.connect(audio_filter1,(i_demod_mixer,0))
fg.connect(src,(i_demod_mixer,1))
fg.connect(i_demod_mixer,(dst,0))
fg.connect(src, (dst,1))
return fg
def main ():
fg = build_graph()
fg.start()
raw_input ('Press Enter to quit')
fg.stop()
if __name__ == '__main__':
main ()
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