I have been trying to receive ATSC signals using USRP and do the signal
processing in Matlab.I am using a 22dB gain indoor antenna. Going
through old discussions here,I found that
$ ./usrp_rx_cfile -R b -d 8 -f 701M -N 40M -g 65 output.dat
can be used to receive the required frequency at a set decimation rate
of 8 and 16-bit binary data is stored in the output file that can be
read into matlab for further processing.
I am a little confused about the data rates and BW stuff. The symbol
rate for ATSC is about 10.76symbols/sec which when VSBd can be fitted
into a 6Mhz BW.
I understand that the signal out of the tuner is sampled at
64Msamples/sec and is down-converted to baseband and decimated by 8
loading the std_4rx_0tx.rbf file in the fpga. So with a 6Msymbols/sec
sampled at 64M samples/sec we get 10.7samples per symbol(64/6) which
when decimated by 8 would leave us with less than 2 samples per
symbol(required by Nyquist). Are we not getting aliasing by doing this?
If I set the decimation rate to 4, I get a lot of overruns. Can somebody
please help me with the math of the signal flow or suggest a