Everything except for the USRP1 has dual halfbands for both TX and RX, including the B100. One of the big advantages of the B100 over the USRP1 is that it uses nearly all the same FPGA code as the USRP2, N2x0, and E1x0, so they all support the same DSP features.
USRP1 has a smaller FPGA from a different manufacturer which uses a separate code base. It only has 1 RX halfband and no TX halfband. Matt On Tue, Oct 25, 2011 at 1:52 AM, Mathias Coinchon <coinc...@yahoo.com>wrote: > Dear Matt, > > I come back on your answer about halfband filter for TX. > Which USRP models do have now halfband filters for TX ? Does the new B100 > has it ? > > Thank you > > Best regards > > Mathias > > ------------------------------ > *De :* Matt Ettus <m...@ettus.com> > *À :* Mathias Coinchon <coinc...@yahoo.com> > *Envoyé le :* Mercredi 4 Août 2010 15h55 > *Objet :* Re: Re : [Discuss-gnuradio] spurious sidelobes with WBX > > > On the USRP1, the TX only has CIC filters, not halfband. CIC filters > have some rolloff (which you see), and they do not perfectly remove the > aliases. You can significantly reduce this effect by interpolating the > signal more in the host and correspondingly less in the USRP. This will > move the passbands further out and reduce the amplitude of those sidelobes. > > The USRP2 does not have this problem, since it has halfband filters. As > long as you use an interpolation rate that is a multiple of 2 you will > get their benefit. > > Matt > > > > On 08/04/2010 05:51 AM, Mathias Coinchon wrote: > > Hi, > > > > Thank you for your answer. However I am not sure to understand how you > > changed your ant-alias filter because this is something that is > > implemented in the USRP FPGA isn't it ? > > > > As I said when monitoring the baseband IQ signal produced by the > > modulator beofre going to USRP, I don't see these sidelobes, they only > > appear after USRP. > > Is it some rounding problem ? and where does this aliasing come from as > > the signal is centered on 0Hz with no further energy after +/- 750Hz. A > > sampling frequency of 3.2MHz (complex) should be enough. I can try use a > > lower interpolation and so use 4MHz instead of 3.2MHz. > > > > > > Best regards > > > > Mathias > > > > > > ------------------------------------------------------------------------ > > *De :* Charles Brain <chbr...@btinternet.com> > > *À :* Mathias Coinchon <coinc...@yahoo.com> > > *Cc :* gnuradio <discuss-gnuradio@gnu.org> > > *Envoyé le :* Mer 4 août 2010, 8h 32min 40s > > *Objet :* Re: [Discuss-gnuradio] spurious sidelobes with WBX > > > > On 03/08/2010 21:50, Mathias Coinchon wrote: > >> Hello, > >> > >> I am using the USRP1 + WBX to create a DAB OFDM signal (1.5MHz > bandwidth) in VHF > >> band. > >> The sampling rate used is 3.2MHz (interpolation 40) > >> > >> However, there's something I don't understand. On the picture attached, > you can > >> see 2 spurious sidelobs that appear at about 2.5MHz from the center (red > arrow). > >> > >> They are not present when monitoring the spectrum of the baseband IQ > signal > >> before going to USRP. > >> > >> They also don't appear when sending a tone signal. > >> > >> Is there any explanation for this ? and any hint to avoid or reduce it ? > >> > >> Thank you for your help. > >> > >> Mathias Coinchon > >> opendigitalradio.org > >> > >> > >> _______________________________________________ > >> Discuss-gnuradio mailing list > >> Discuss-gnuradio@gnu.org > >> http://lists.gnu.org/mailman/listinfo/discuss-gnuradio > > > > It looks a bit like this doesn't it. > > http://tinyurl.com/2vhge7j > > These ears on my DVB-T signal were caused by aliasing. > > when I changed my anti-alias filter they went away > > > > - Charles > > * > > * > > > > > > > > _______________________________________________ > > Discuss-gnuradio mailing list > > Discuss-gnuradio@gnu.org > > http://lists.gnu.org/mailman/listinfo/discuss-gnuradio > > > >
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