Gnuradio DAB constellation using gr-dab and USRP
From Opendigitalradio
Plot in live the constellation diagram of a received DAB signal using gr-dab and USRP.
Contents |
Pre-requisites
- USRP or baseband recording from a file
- WBX daughterboard or modified RFX400 (TVRX daughterboard has too much phase noise and cannot be used)
- Linux PC with Gnuradio source (>=3.2)
- gr-dab tools
Installation
- Download source code of gnuradio and gr-dab tools
- Patch peak detector of gnuradio source code with patch/not-applied-in-trunk of gr-dab
- Patch "dab_rx_constellation.py" with patch below
- Configure, compile and install gnuradio and then gr-dab tools.
- If you want to use a separate gnuradio installation from the original one, follow steps here to have multiple gnuradio installation on your machine
Usage
(dab_rx_constellation.py -h)
Usage: dab_rx_constellation.py: [options] <filename> Options: -h, --help show this help message and exit -m DAB_MODE, --dab-mode=DAB_MODE DAB mode [default=1] -F, --filter-input Enable FFT filter at input -c, --correct-ffe do fine frequency correction -u, --correct-ffe-usrp do fine frequency correction by retuning the USRP instead of in software -e, --equalize-magnitude do magnitude equalization -s RESAMPLE_FIXED, --resample-fixed=RESAMPLE_FIXED resample by a fixed factor (fractional interpolation) -S, --autocorrect-sample-rate Estimate sample rate offset and resample (dynamic fractional interpolation) -R RX_SUBDEV_SPEC, --rx-subdev-spec=RX_SUBDEV_SPEC select USRP Rx side A or B [default=A] -f FREQ, --freq=FREQ set frequency to FREQ [default=227360000.0] -r SAMPLE_RATE, --sample-rate=SAMPLE_RATE set sample rate to SAMPLE_RATE [default=2000000] -d DECIM, --decim=DECIM set decimation rate to DECIM [default=32] -g RX_GAIN, --rx-gain=RX_GAIN set receive gain in dB (default is midpoint) -v, --verbose verbose output
Example for plotting the constellation of an ensemble on 223.936MHz:
dab_rx_constellation.py -R A -f 223936000 -c -e -S
dab_rx_constellation.py patch
Index: dab_rx_constellation.py =================================================================== --- dab_rx_constellation.py (revision 203) +++ dab_rx_constellation.py (working copy) @@ -91,8 +91,8 @@ self.demod = dab.ofdm_demod(self.dab_params, self.rx_params, verbose=self.verbose) self.v2s = gr.vector_to_stream(gr.sizeof_gr_complex, self.dab_params.num_carriers) - self.scope = scopesink2.constellation_sink(self.panel, title="DAB constellation sink", sample_rate=self.dab_params.sample_rate, frame_decim=3) - self.scope.win.set_marker("plus") + self.scope = scopesink2.scope_sink_c(self.panel, title="DAB constellation sink", sample_rate=self.dab_params.sample_rate, frame_decim=3) + # self.scope.win.set_marker("plus") # self.sink = gr.null_sink(gr.sizeof_char*self.dab_params.num_carriers/4) self.trigsink = gr.null_sink(gr.sizeof_char)