[Discuss-gnuradio] OFDM / DAB demodulation

[Jens Elsner]

Good morning,

I sampled a local DAB radio station at 225.648 MHz, decimation factor 32
with the USRP/tvrx.

DAB is using COFDM with pi/4-DPSK on 1536 subcarriers (see www.etsi.com, 
standard
EN300401 for details). I wrote some Matlab code to demodulate the
signal. The data is resampled from 2 MHz (URSP) to 2.048 MHz (DAB Standard).
A frequency offset is compensated manually. 

It works so far, only one problem arises: The I/Q signal diagram jumps
and jitters randomly by up to pi/8. What could be the problem? I am
absolutely clueless - the frequency offset is compensated perfectly.

My ultimate goal is to implement OFDM de/modulation and a DAB receiver
in gnuradio.

Greetings,
Jens