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Complete redesign of the BPSK decoder 

This commit implements a new approach for the BPSK AX.25 decoding. It
seems that the GNU Radio equalizers (both CMA and LMS) are not ideal for
bursty transmissions. After they loose 'lock', they tend to converge
quite slow again.

The equalizing problem is again solved using an AGC2 block. However, the
placement of this block is quite critical. In older versions the AGC was
placed several steps after resampling and filtering. This resulted to
poor equalization and noise increase. Now the AGC is placed as early as
possible when the signal has a large span.
This commit is contained in:
Manolis Surligas 2018-11-27 16:55:59 +02:00
parent ab022f1058
commit 1bc575cc25
2 changed files with 538 additions and 253 deletions
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697
apps/flowgraphs/bpsk_ax25.grc
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94
apps/flowgraphs/satnogs_bpsk_ax25.py
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@ -5,12 +5,14 @@
# Title: satnogs_bpsk_ax25
# Author: Manolis Surligas (surligas@gmail.com), Patrick Dohmen (DL4PD)
# Description: BPSK AX.25 decoder
# Generated: Sat Nov 24 23:25:36 2018
# Generated: Tue Nov 27 16:45:38 2018
##################################################
from gnuradio import analog
from gnuradio import blocks
from gnuradio import digital
from gnuradio import eng_notation
from gnuradio import filter
from gnuradio import gr
from gnuradio.eng_option import eng_option
from gnuradio.filter import firdes
@ -24,7 +26,7 @@ import time
class satnogs_bpsk_ax25(gr.top_block):
def __init__(self, antenna=satnogs.not_set_antenna, baudrate=9600.0, bb_gain=satnogs.not_set_rx_bb_gain, decoded_data_file_path='/tmp/.satnogs/data/data', dev_args=satnogs.not_set_dev_args, doppler_correction_per_sec=1000, enable_iq_dump=0, file_path='test.wav', if_gain=satnogs.not_set_rx_if_gain, iq_file_path='/tmp/iq.dat', lo_offset=100e3, ppm=0, rf_gain=satnogs.not_set_rx_rf_gain, rigctl_port=4532, rx_freq=100e6, rx_sdr_device='usrpb200', samp_rate_rx=satnogs.not_set_samp_rate_rx, udp_IP='127.0.0.1', udp_port=16887, waterfall_file_path='/tmp/waterfall.dat'):
def __init__(self, antenna=satnogs.not_set_antenna, baudrate=9600.0, bb_gain=satnogs.not_set_rx_bb_gain, decoded_data_file_path='/tmp/.satnogs/data/data', dev_args=satnogs.not_set_dev_args, doppler_correction_per_sec=1000, enable_iq_dump=0, file_path='test.wav', if_gain=satnogs.not_set_rx_if_gain, iq_file_path='/tmp/iq.dat', lo_offset=100e3, ppm=0, rf_gain=satnogs.not_set_rx_rf_gain, rigctl_port=4532, rx_freq=100e6, rx_sdr_device='usrpb200', samp_rate_rx=satnogs.not_set_samp_rate_rx, udp_IP='127.0.0.1', udp_port=16887, waterfall_file_path='/tmp/waterfall.dat', excess_bw=0.35, max_cfo=1000.0):
gr.top_block.__init__(self, "satnogs_bpsk_ax25")
##################################################
@ -50,13 +52,15 @@ class satnogs_bpsk_ax25(gr.top_block):
self.udp_IP = udp_IP
self.udp_port = udp_port
self.waterfall_file_path = waterfall_file_path
self.excess_bw = excess_bw
self.max_cfo = max_cfo
##################################################
# Variables
##################################################
self.sps = sps = 2
self.nfilts = nfilts = 11
self.rrc_taps = rrc_taps = firdes.root_raised_cosine(nfilts, nfilts, 1.0/float(sps), 0.35, 11*sps*nfilts)
self.sps = sps = 4
self.nfilts = nfilts = 32
self.rrc_taps = rrc_taps = firdes.root_raised_cosine(nfilts, nfilts, 1.0/float(sps), excess_bw, 11*sps*nfilts)
self.bpsk_constellation = bpsk_constellation = digital.constellation_bpsk().base()
@ -75,7 +79,7 @@ class satnogs_bpsk_ax25(gr.top_block):
self.satnogs_ax25_decoder_bm_0_0 = satnogs.ax25_decoder_bm('GND', 0, True, False, 1024)
self.satnogs_ax25_decoder_bm_0 = satnogs.ax25_decoder_bm('GND', 0, True, True, 1024)
self.pfb_arb_resampler_xxx_0_0 = pfb.arb_resampler_ccf(
(1.0 * sps*baudrate)/audio_samp_rate,
(1.0 * sps*baudrate)/satnogs.handle_samp_rate_rx(rx_sdr_device, samp_rate_rx),
taps=None,
flt_size=32)
self.pfb_arb_resampler_xxx_0_0.declare_sample_delay(0)
@ -99,15 +103,20 @@ class satnogs_bpsk_ax25(gr.top_block):
self.osmosdr_source_0.set_antenna(satnogs.handle_rx_antenna(rx_sdr_device, antenna), 0)
self.osmosdr_source_0.set_bandwidth(satnogs.handle_samp_rate_rx(rx_sdr_device, samp_rate_rx), 0)
self.digital_pfb_clock_sync_xxx_0 = digital.pfb_clock_sync_ccf(sps, 2.0 * math.pi / 100.0, (rrc_taps), nfilts, nfilts/2, 1.5, 1)
self.digital_lms_dd_equalizer_cc_1 = digital.lms_dd_equalizer_cc(11, 0.001, 1, bpsk_constellation)
self.digital_costas_loop_cc_0 = digital.costas_loop_cc(2.0 * math.pi / 100.0, 2, False)
self.digital_cma_equalizer_cc_0 = digital.cma_equalizer_cc(11, 1, 0.001, 1)
self.digital_binary_slicer_fb_0 = digital.binary_slicer_fb()
self.low_pass_filter_0_0 = filter.fir_filter_ccf(1, firdes.low_pass(
1, audio_samp_rate, ((1.0 + excess_bw) * baudrate/2.0) + max_cfo, baudrate / 16.0, firdes.WIN_HAMMING, 6.76))
self.low_pass_filter_0 = filter.fir_filter_ccf(1, firdes.low_pass(
1, sps*baudrate, ((1.0 + excess_bw) * baudrate/2.0) + max_cfo, baudrate / 16.0, firdes.WIN_HAMMING, 6.76))
self.digital_pfb_clock_sync_xxx_0 = digital.pfb_clock_sync_ccf(sps, 2.0 * math.pi/100.0, (rrc_taps), nfilts, nfilts/2, 1.5, 1)
self.digital_costas_loop_cc_0_0 = digital.costas_loop_cc(2.0 * math.pi / 100.0, 2, True)
self.digital_constellation_receiver_cb_0 = digital.constellation_receiver_cb(bpsk_constellation, 2.0 * math.pi/100.0, -0.25, 0.25)
self.blocks_rotator_cc_0_0 = blocks.rotator_cc(2.0 * math.pi * (1200.0 / audio_samp_rate))
self.blocks_rotator_cc_0 = blocks.rotator_cc(-2.0 * math.pi * (lo_offset / satnogs.handle_samp_rate_rx(rx_sdr_device, samp_rate_rx)))
self.blocks_complex_to_real_0_0 = blocks.complex_to_real(1)
self.blocks_complex_to_real_0 = blocks.complex_to_real(1)
self.analog_agc2_xx_0_0 = analog.agc2_cc(0.01, 0.001, 0.015, 1.0)
self.analog_agc2_xx_0_0.set_max_gain(65536)
self.analog_agc2_xx_0 = analog.agc2_cc(1e-3, 1e-3, 0.5, 1.0)
self.analog_agc2_xx_0.set_max_gain(65536)
@ -119,22 +128,23 @@ class satnogs_bpsk_ax25(gr.top_block):
self.msg_connect((self.satnogs_ax25_decoder_bm_0_0, 'pdu'), (self.satnogs_frame_file_sink_0_1_0, 'frame'))
self.msg_connect((self.satnogs_ax25_decoder_bm_0_0, 'pdu'), (self.satnogs_udp_msg_sink_0_0, 'in'))
self.msg_connect((self.satnogs_tcp_rigctl_msg_source_0, 'freq'), (self.satnogs_coarse_doppler_correction_cc_0, 'freq'))
self.connect((self.analog_agc2_xx_0, 0), (self.pfb_arb_resampler_xxx_0_0, 0))
self.connect((self.analog_agc2_xx_0_0, 0), (self.low_pass_filter_0_0, 0))
self.connect((self.blocks_complex_to_real_0, 0), (self.satnogs_ogg_encoder_0, 0))
self.connect((self.blocks_complex_to_real_0_0, 0), (self.digital_binary_slicer_fb_0, 0))
self.connect((self.blocks_rotator_cc_0, 0), (self.satnogs_coarse_doppler_correction_cc_0, 0))
self.connect((self.blocks_rotator_cc_0_0, 0), (self.blocks_complex_to_real_0, 0))
self.connect((self.digital_binary_slicer_fb_0, 0), (self.satnogs_ax25_decoder_bm_0, 0))
self.connect((self.digital_binary_slicer_fb_0, 0), (self.satnogs_ax25_decoder_bm_0_0, 0))
self.connect((self.digital_cma_equalizer_cc_0, 0), (self.digital_lms_dd_equalizer_cc_1, 0))
self.connect((self.digital_costas_loop_cc_0, 0), (self.blocks_complex_to_real_0_0, 0))
self.connect((self.digital_lms_dd_equalizer_cc_1, 0), (self.digital_costas_loop_cc_0, 0))
self.connect((self.digital_pfb_clock_sync_xxx_0, 0), (self.digital_cma_equalizer_cc_0, 0))
self.connect((self.digital_constellation_receiver_cb_0, 0), (self.satnogs_ax25_decoder_bm_0, 0))
self.connect((self.digital_constellation_receiver_cb_0, 0), (self.satnogs_ax25_decoder_bm_0_0, 0))
self.connect((self.digital_costas_loop_cc_0_0, 0), (self.digital_pfb_clock_sync_xxx_0, 0))
self.connect((self.digital_pfb_clock_sync_xxx_0, 0), (self.digital_constellation_receiver_cb_0, 0))
self.connect((self.low_pass_filter_0, 0), (self.digital_costas_loop_cc_0_0, 0))
self.connect((self.low_pass_filter_0_0, 0), (self.blocks_rotator_cc_0_0, 0))
self.connect((self.osmosdr_source_0, 0), (self.blocks_rotator_cc_0, 0))
self.connect((self.pfb_arb_resampler_xxx_0, 0), (self.blocks_rotator_cc_0_0, 0))
self.connect((self.pfb_arb_resampler_xxx_0, 0), (self.pfb_arb_resampler_xxx_0_0, 0))
self.connect((self.pfb_arb_resampler_xxx_0, 0), (self.analog_agc2_xx_0_0, 0))
self.connect((self.pfb_arb_resampler_xxx_0, 0), (self.satnogs_iq_sink_0, 0))
self.connect((self.pfb_arb_resampler_xxx_0, 0), (self.satnogs_waterfall_sink_0, 0))
self.connect((self.pfb_arb_resampler_xxx_0_0, 0), (self.digital_pfb_clock_sync_xxx_0, 0))
self.connect((self.pfb_arb_resampler_xxx_0_0, 0), (self.low_pass_filter_0, 0))
self.connect((self.satnogs_coarse_doppler_correction_cc_0, 0), (self.analog_agc2_xx_0, 0))
self.connect((self.satnogs_coarse_doppler_correction_cc_0, 0), (self.pfb_arb_resampler_xxx_0, 0))
def get_antenna(self):
@ -149,7 +159,9 @@ class satnogs_bpsk_ax25(gr.top_block):
def set_baudrate(self, baudrate):
self.baudrate = baudrate
self.pfb_arb_resampler_xxx_0_0.set_rate((1.0 * self.sps*self.baudrate)/self.audio_samp_rate)
self.pfb_arb_resampler_xxx_0_0.set_rate((1.0 * self.sps*self.baudrate)/satnogs.handle_samp_rate_rx(self.rx_sdr_device, self.samp_rate_rx))
self.low_pass_filter_0_0.set_taps(firdes.low_pass(1, self.audio_samp_rate, ((1.0 + self.excess_bw) * self.baudrate/2.0) + self.max_cfo, self.baudrate / 16.0, firdes.WIN_HAMMING, 6.76))
self.low_pass_filter_0.set_taps(firdes.low_pass(1, self.sps*self.baudrate, ((1.0 + self.excess_bw) * self.baudrate/2.0) + self.max_cfo, self.baudrate / 16.0, firdes.WIN_HAMMING, 6.76))
def get_bb_gain(self):
return self.bb_gain
@ -242,6 +254,7 @@ class satnogs_bpsk_ax25(gr.top_block):
def set_rx_sdr_device(self, rx_sdr_device):
self.rx_sdr_device = rx_sdr_device
self.pfb_arb_resampler_xxx_0_0.set_rate((1.0 * self.sps*self.baudrate)/satnogs.handle_samp_rate_rx(self.rx_sdr_device, self.samp_rate_rx))
self.pfb_arb_resampler_xxx_0.set_rate(self.audio_samp_rate/satnogs.handle_samp_rate_rx(self.rx_sdr_device, self.samp_rate_rx))
self.osmosdr_source_0.set_sample_rate(satnogs.handle_samp_rate_rx(self.rx_sdr_device, self.samp_rate_rx))
self.osmosdr_source_0.set_gain(satnogs.handle_rx_rf_gain(self.rx_sdr_device, self.rf_gain), 0)
@ -256,6 +269,7 @@ class satnogs_bpsk_ax25(gr.top_block):
def set_samp_rate_rx(self, samp_rate_rx):
self.samp_rate_rx = samp_rate_rx
self.pfb_arb_resampler_xxx_0_0.set_rate((1.0 * self.sps*self.baudrate)/satnogs.handle_samp_rate_rx(self.rx_sdr_device, self.samp_rate_rx))
self.pfb_arb_resampler_xxx_0.set_rate(self.audio_samp_rate/satnogs.handle_samp_rate_rx(self.rx_sdr_device, self.samp_rate_rx))
self.osmosdr_source_0.set_sample_rate(satnogs.handle_samp_rate_rx(self.rx_sdr_device, self.samp_rate_rx))
self.osmosdr_source_0.set_bandwidth(satnogs.handle_samp_rate_rx(self.rx_sdr_device, self.samp_rate_rx), 0)
@ -279,20 +293,38 @@ class satnogs_bpsk_ax25(gr.top_block):
def set_waterfall_file_path(self, waterfall_file_path):
self.waterfall_file_path = waterfall_file_path
def get_excess_bw(self):
return self.excess_bw
def set_excess_bw(self, excess_bw):
self.excess_bw = excess_bw
self.set_rrc_taps(firdes.root_raised_cosine(self.nfilts, self.nfilts, 1.0/float(self.sps), self.excess_bw, 11*self.sps*self.nfilts))
self.low_pass_filter_0_0.set_taps(firdes.low_pass(1, self.audio_samp_rate, ((1.0 + self.excess_bw) * self.baudrate/2.0) + self.max_cfo, self.baudrate / 16.0, firdes.WIN_HAMMING, 6.76))
self.low_pass_filter_0.set_taps(firdes.low_pass(1, self.sps*self.baudrate, ((1.0 + self.excess_bw) * self.baudrate/2.0) + self.max_cfo, self.baudrate / 16.0, firdes.WIN_HAMMING, 6.76))
def get_max_cfo(self):
return self.max_cfo
def set_max_cfo(self, max_cfo):
self.max_cfo = max_cfo
self.low_pass_filter_0_0.set_taps(firdes.low_pass(1, self.audio_samp_rate, ((1.0 + self.excess_bw) * self.baudrate/2.0) + self.max_cfo, self.baudrate / 16.0, firdes.WIN_HAMMING, 6.76))
self.low_pass_filter_0.set_taps(firdes.low_pass(1, self.sps*self.baudrate, ((1.0 + self.excess_bw) * self.baudrate/2.0) + self.max_cfo, self.baudrate / 16.0, firdes.WIN_HAMMING, 6.76))
def get_sps(self):
return self.sps
def set_sps(self, sps):
self.sps = sps
self.set_rrc_taps(firdes.root_raised_cosine(self.nfilts, self.nfilts, 1.0/float(self.sps), 0.35, 11*self.sps*self.nfilts))
self.pfb_arb_resampler_xxx_0_0.set_rate((1.0 * self.sps*self.baudrate)/self.audio_samp_rate)
self.set_rrc_taps(firdes.root_raised_cosine(self.nfilts, self.nfilts, 1.0/float(self.sps), self.excess_bw, 11*self.sps*self.nfilts))
self.pfb_arb_resampler_xxx_0_0.set_rate((1.0 * self.sps*self.baudrate)/satnogs.handle_samp_rate_rx(self.rx_sdr_device, self.samp_rate_rx))
self.low_pass_filter_0.set_taps(firdes.low_pass(1, self.sps*self.baudrate, ((1.0 + self.excess_bw) * self.baudrate/2.0) + self.max_cfo, self.baudrate / 16.0, firdes.WIN_HAMMING, 6.76))
def get_nfilts(self):
return self.nfilts
def set_nfilts(self, nfilts):
self.nfilts = nfilts
self.set_rrc_taps(firdes.root_raised_cosine(self.nfilts, self.nfilts, 1.0/float(self.sps), 0.35, 11*self.sps*self.nfilts))
self.set_rrc_taps(firdes.root_raised_cosine(self.nfilts, self.nfilts, 1.0/float(self.sps), self.excess_bw, 11*self.sps*self.nfilts))
def get_rrc_taps(self):
return self.rrc_taps
@ -312,8 +344,8 @@ class satnogs_bpsk_ax25(gr.top_block):
def set_audio_samp_rate(self, audio_samp_rate):
self.audio_samp_rate = audio_samp_rate
self.pfb_arb_resampler_xxx_0_0.set_rate((1.0 * self.sps*self.baudrate)/self.audio_samp_rate)
self.pfb_arb_resampler_xxx_0.set_rate(self.audio_samp_rate/satnogs.handle_samp_rate_rx(self.rx_sdr_device, self.samp_rate_rx))
self.low_pass_filter_0_0.set_taps(firdes.low_pass(1, self.audio_samp_rate, ((1.0 + self.excess_bw) * self.baudrate/2.0) + self.max_cfo, self.baudrate / 16.0, firdes.WIN_HAMMING, 6.76))
self.blocks_rotator_cc_0_0.set_phase_inc(2.0 * math.pi * (1200.0 / self.audio_samp_rate))
@ -380,6 +412,12 @@ def argument_parser():
parser.add_option(
"", "--waterfall-file-path", dest="waterfall_file_path", type="string", default='/tmp/waterfall.dat',
help="Set waterfall_file_path [default=%default]")
parser.add_option(
"", "--excess-bw", dest="excess_bw", type="eng_float", default=eng_notation.num_to_str(0.35),
help="Set excess_bw [default=%default]")
parser.add_option(
"", "--max-cfo", dest="max_cfo", type="eng_float", default=eng_notation.num_to_str(1000.0),
help="Set max_cfo [default=%default]")
return parser
@ -387,7 +425,7 @@ def main(top_block_cls=satnogs_bpsk_ax25, options=None):
if options is None:
options, _ = argument_parser().parse_args()
tb = top_block_cls(antenna=options.antenna, baudrate=options.baudrate, bb_gain=options.bb_gain, decoded_data_file_path=options.decoded_data_file_path, dev_args=options.dev_args, doppler_correction_per_sec=options.doppler_correction_per_sec, enable_iq_dump=options.enable_iq_dump, file_path=options.file_path, if_gain=options.if_gain, iq_file_path=options.iq_file_path, lo_offset=options.lo_offset, ppm=options.ppm, rf_gain=options.rf_gain, rigctl_port=options.rigctl_port, rx_freq=options.rx_freq, rx_sdr_device=options.rx_sdr_device, samp_rate_rx=options.samp_rate_rx, udp_IP=options.udp_IP, udp_port=options.udp_port, waterfall_file_path=options.waterfall_file_path)
tb = top_block_cls(antenna=options.antenna, baudrate=options.baudrate, bb_gain=options.bb_gain, decoded_data_file_path=options.decoded_data_file_path, dev_args=options.dev_args, doppler_correction_per_sec=options.doppler_correction_per_sec, enable_iq_dump=options.enable_iq_dump, file_path=options.file_path, if_gain=options.if_gain, iq_file_path=options.iq_file_path, lo_offset=options.lo_offset, ppm=options.ppm, rf_gain=options.rf_gain, rigctl_port=options.rigctl_port, rx_freq=options.rx_freq, rx_sdr_device=options.rx_sdr_device, samp_rate_rx=options.samp_rate_rx, udp_IP=options.udp_IP, udp_port=options.udp_port, waterfall_file_path=options.waterfall_file_path, excess_bw=options.excess_bw, max_cfo=options.max_cfo)
tb.start()
tb.wait()