Re: [Discuss-gnuradio] OFDM / DAB demodulation

[Clark Pope]

Resample is okay, but beware of any other filter operations you are doing on 
the data in a block-wise manner, e.g. chunks. You have to remember to save 
the initial conditions:

[chunk_filt, z] = filter(b,a,chunk,z);

This would cause phase discontinuities at the edges of each block.

-Clark

> From: Jens Elsner <address@hidden>
> To: address@hidden
> Subject: Re: [Discuss-gnuradio] OFDM / DAB demodulation
> Date: Sat, 1 Apr 2006 10:48:29 +0200
>
> To resample, I used the Matlab "resample" function
>
> chunk_resamp = resample(chunk, 2048, 2000);
>
> It's basically an FIR low-pass - phase is linear.
>
> I'll try again today without resampling, but then the timing is
> pretty much screwed up.
>
> Jens
>
> On Fri, Mar 31, 2006 at 04:28:14PM -0800, Eric Blossom wrote:
> > On Fri, Mar 31, 2006 at 05:10:40PM -0500, Clark Pope wrote:
> > > 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
> > >
> > > >>
> > > >> 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.
> >
> > How did you resample from 2.000MHz to 2.048 MHz?
> >
> > Eric
>
>
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