This is a set of script to do correlation measurement measurements of a DAB signal. These scripts can be used to do channel impulse response measurements using a RTLSDR receiver.
Right now there are three scripts:
correlate_with_ref.py: Finds the NULL symbol of an IQ file, and runs correlations against the known phase reference to find the components.
simulate_channel.py: Reads an I/Q file generated by ODR-DabMod and adds some additional components, somehow equivalent to signal reflexions. Each reflexion has a delay and an amplitude factor.
cir_measure.py: Runs a small webserver that does the correlation all the time and updates a webpage
The image shows the received CIR of a real DAB signal captured with the RTLSDR.
To run the webserver on all network interfaces, receiving on 202.928MHz:
./cir_measure.py --host 0.0.0.0 --port 8080 --freq 202928000
More options are available (gain, number of samples), see the help with
To read in a recording using a RTL-SDR receiver, use:
rtl_sdr -f 188928000 -s 2048000 -g 20 -S - | \ dd of=DAB_9A_10_u8_G20.iq bs=2 count=1966080
replace 1966080 (ten Mode 1 transmission frames) by a larger value if you want.
Then feed the data to the script
./correlate_with_ref.py u8 DAB_9A_10_u8_G20.iq
librtlsdr and its tools.
Python with NumPy and matplotlib.
The iq files must be complex float or interleaved unsigned 8-bit.
MIT. See LICENCE for details.
Improve the sync code, to make sure we align the pictures each time. Align on the strongest peak instead of the NULL symbol.
Generate long-term visualisations, to see if there is a change over several days.
Oversample 2x or 4x to get finer time resolution.
Make sure rtl_tcp quits properly on ctrl-c.