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 <[EMAIL PROTECTED]>
To: discuss-gnuradio@gnu.org
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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