Re: [Discuss-gnuradio] OFDM / DAB demodulation

[Clark Pope]

I would doubt that unless your USRP is defective. The phase noise should 
only become a major factor at baud rates below about 10 kbaud.

What's the actual bandwidth of the DAB signal? Did you try collecting at 4 
MSPS and then downsampling to the FFT sample rate? Maybe the CIC or 
compensation filter transition are distorting the final result.

-Clark

> From: Jens Elsner <address@hidden>
> To: address@hidden
> Subject: Re: [Discuss-gnuradio] OFDM / DAB demodulation
> Date: Fri, 31 Mar 2006 19:28:38 +0200
>
> After some thinking: Could this be phase noise? If it is, which
> oscillator is at fault? The TVRX frontend? The max. phase jitter equals
> roughly 100 Hz.
>
> On Fri, Mar 31, 2006 at 05:08:54PM +0200, Jens Elsner wrote:
> > 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
> >
> >
> >
> > _______________________________________________
> > Discuss-gnuradio mailing list
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> > http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
>
>
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