Forgot to answer your questions: The subcarrier spacing is 1 KHz, 1536+DC Carrier (unused) = 1.537 MHz I sampled 2 MHz (USRP, dec 32). Then I sampled up to 2.048 MHz since 1/2.048MHz is the basic timing unit in the standard.
I tried again without resampling - the random phase jitter is still there. Plus the timing problem - the standard requires 2.048 MHz to I get decimal offset values. For example at the 2.000 MHz the guard intervall has the length 492.1875. Do you think downsampling will work better than upsampling? I'll try that tomorrow. 3/31/2006, "Clark Pope" <[EMAIL PROTECTED]> вы писали: >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 <[EMAIL PROTECTED]> >>To: discuss-gnuradio@gnu.org >>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 >> > Discuss-gnuradio@gnu.org >> > http://lists.gnu.org/mailman/listinfo/discuss-gnuradio >> >> >>_______________________________________________ >>Discuss-gnuradio mailing list >>Discuss-gnuradio@gnu.org >>http://lists.gnu.org/mailman/listinfo/discuss-gnuradio > >_________________________________________________________________ >Is your PC infected? Get a FREE online computer virus scan from McAfee® >Security. http://clinic.mcafee.com/clinic/ibuy/campaign.asp?cid=3963 > _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
