Hi Snehasish, A few thoughts...
> 25msps and tried dividing it into 16 channels. I should have returned 625kspsx2 sample rate each channel Based on your screen shot I'm guessing you started with 10 Msps and used 16 channels to get 625 kHz channel spacing (with 1250 ksps per channel). Is that correct? > But you can see the snaphshots, if a tune into 955.4MHz and try to get a channel on index 0 ie the center freq, it works well and I am able to decode GSM Burst from it. But if I try to add index 2(which is 955.8MHz), the amplitude in the spectrum falls and also I am not able to decode any GSM burst Is it correct that your "index 2" center frequency is targetting 400 kHz offset from the center frequency? If so, I dont expect this would work. Using a channel spacing of 625 kHz, the closest channel you could receive next to 955.4 MHz would be 956.025 MHz. Based on your screenshot it actually seems like the peak energy you're looking for may be lower than the channel frequency by about 200 kHz? This is one downside of the polyphase channelizer in this particular implementation. The channel outputs are consistently spaced and cannot be changed except by moving the sample rate, center frequency, or number of channels. EJ On Fri, Apr 24, 2020 at 8:31 AM Snehasish Kar <snehasish....@live.com> wrote: > Hello EJ > > I tried using your channelizer. Its really a helpful module. The challenge > I faced when i tried using it with a input sample rate of 25msps and tried > dividing it into 16 channels. I should have returned 625kspsx2 sample rate > each channel. But you can see the snaphshots, if a tune into 955.4MHz and > try to get a channel on index 0 ie the center freq, it works well and I am > able to decode GSM Burst from it. But if I try to add index 2(which is > 955.8MHz), the amplitude in the spectrum falls and also I am not able to > decode any GSM burst. The same happens when i tune 955.8MHz and try to get > index 14(ie 955.4MHz), I don't see the spectrum, the same happens for 128 > and 256 channel (input sample rate 50msps). Can you please let me know if I > am going wrong somewhere. I have attached the snapshots and flow graph > for your reference. My uhd version is UHD_3.14.0.0-0-unknown. > > Regards > Snehasish > > > ------------------------------ > *From:* EJ Kreinar <ejkrei...@gmail.com> > *Sent:* Friday, April 24, 2020 4:22 PM > *To:* Snehasish Kar <snehasish....@live.com> > *Cc:* Jonathon Pendlum <jonathon.pend...@ettus.com>; > USRP-users@lists.ettus.com <usrp-users@lists.ettus.com> > *Subject:* Re: [USRP-users] Fractional downsampling in rfnoc > > Hi Snehasish, > > Since you're already working with theseus-cores, I assume you've found the > rfnoc polyphase channelizer has channel downselection already integrated > into rfnoc and gnuradio (brief write up about it here: > https://www.theseus-cores.com/2019/12/17/rfnoc-deinterleaving-polyphase-channelizer/). > I believe this worked with UHD-3.14 when I tested last December. Wondering > if this works for you or if there's other updates you might need? > > EJ > > On Fri, Apr 24, 2020, 12:56 AM Snehasish Kar via USRP-users < > usrp-users@lists.ettus.com> wrote: > > Hello Jonathon > > I tried building the fractional downsampler again and was successful to > build it in this version of UHD: UHD 4.0.0.rfnoc-devel-409-gec9138eb. Also > there is a channelizer available at > https://github.com/e33b1711/rfnoc-ppchan . But the problem with this > channelizer is, it sends almost 25.6msps samples to the host. Also the > number of packet it sends, creates a overflow in the host even with 10gig > sfp cable. So what I am planning is to make a de-interleaver, which will be > responsible for channel down-selection. Please let me know your thoughts on > this. > > Can you please let me know how to set the packet size on any rfnoc block. > > Regards > Snehasish > ------------------------------ > *From:* Jonathon Pendlum <jonathon.pend...@ettus.com> > *Sent:* Sunday, April 19, 2020 8:58 AM > *To:* Snehasish Kar <snehasish....@live.com> > *Cc:* usrp-users@lists.ettus.com <usrp-users@lists.ettus.com> > *Subject:* Re: [USRP-users] Fractional downsampling in rfnoc > > Hi Snehasish, > > I forgot about that error. I actually made an issue about it on their > repo: https://github.com/SynchronousLabs/rfnoc-SynchronousLabs/issues/2. > Unless they provide an EDIF or their source code, you can only use their > code for simulation. Certainly a disappointing oversight on their part. > > Jonathon > > On Sat, Apr 18, 2020 at 6:21 PM Snehasish Kar <snehasish....@live.com> > wrote: > > Hello Jonathon > > Tried building the fractional downsampler from synchronous labs and have > encountered the following error: > source file was generated for simulation and is not permitted as input to > synthesis > [/home/snehasish/rfnoc-SynchronousLabs/rfnoc/fpga-src/fract_dec_filter.vhd:241995] > > Can you please help me with it. > > Regards > Snehasish > ------------------------------ > *From:* Jonathon Pendlum <jonathon.pend...@ettus.com> > *Sent:* Friday, April 17, 2020 9:22 PM > *To:* Snehasish Kar <snehasish....@live.com> > *Cc:* usrp-users@lists.ettus.com <usrp-users@lists.ettus.com> > *Subject:* Re: [USRP-users] Fractional downsampling in rfnoc > > Hello Snehasish, > > Unfortunately, the standard library of blocks does not have a Fractional > Decimator. Your best bet is to try to use the one made by Synchronous Labs > a few years ago. Their code is on github here: > https://github.com/SynchronousLabs/rfnoc-SynchronousLabs. Since it was > built, RFNoC has had some changes that will need to be fixed, but I think > this is your only option versus writing one from scratch. > > Jonathon > > On Thu, Apr 16, 2020 at 6:35 PM Snehasish Kar via USRP-users < > usrp-users@lists.ettus.com> wrote: > > Hello > > I am trying to use the RFNOC based M/2 channelizer from > https://github.com/theseus-cores/theseus-cores/releases/tag/v1.1.0 . I am > trying to divide 25 MHz spectrum into 124 subchannels each of bandwidth > 200KHz. I am capturing the signal at 200msps and I need to decimate it to > 25.6msps(25MHz/128 channels). Please help me in understanding how this can > be achieved using RFNoC, is there’s any block already defined for > fractional downsampling. > > Thanks & Regards > Snehasish > > Get Outlook for iOS <https://aka.ms/o0ukef> > _______________________________________________ > USRP-users mailing list > USRP-users@lists.ettus.com > http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com > > _______________________________________________ > USRP-users mailing list > USRP-users@lists.ettus.com > http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com > >
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