Thank you so much Ian. This explanation makes it clear to me. Best, Wahhab
On Sun, Dec 31, 2017 at 7:29 PM, Ian Buckley <[email protected]> wrote: > Wahhab, > No USRP supports the configuration you are trying to achieve. > The USRP2 (and N210) have a fixed ADC sample rate of 100MHz. > The B210/E310 uses an oversampling Sigma-delta ADC that can sample as high > as ~650MHZ. It will *always* oversample relative to the "sample rate" you > request. > The X310 uses a programmable sample rate but was designed and tested only > for sample rates ~100Mhz->200MHz. > Currently sold daughter cards all have fixed baseband analog LPF of either > 40MHz or 160MHz bandwidth with the intent of removing analog aliasing. The > sole exception is Basic RX as already been pointed out. > > You could experiment with aliasing in the digital domain by using the > USRP(s) you have available at their highest capture bandwidth and > decimating without filtering in your own SDR application. > > If you really need to alias in the analog domain then you need to build > your own H/W, or more easily, purchase a reference design for a wideband > ADC from ADI/TI etc. > > -Ian > > > On Dec 30, 2017, at 3:35 PM, Ron Economos via USRP-users < > [email protected]> wrote: > > The bladeRF SDR can easily be configured to show aliasing. Here's a 6 MHz > wide OFDM signal with the transmit filter set to 28 MHz. You can also see > the sin(x)/x response of the DAC. > <alias28.png> > > Ron > > On 12/30/2017 03:14 PM, Jeff Long via USRP-users wrote: > > If you're trying to recreate Mike Ossmann's Bluetooth aliasing experiment, > he explains what he did here: > > https://github.com/greatscottgadgets/gr-bluetooth/blob/master/doc/ > README.aliasing > > On 12/29/2017 08:26 PM, Wahhab Albazrqaoe via USRP-users wrote: > > Thank you Jeff.. > > Are these filters in software? Or fpga? Is there any function that we play > with to get aliasing? i.e. how to disable such filters? > > > Thank you > > Wahhab > > > The B2XX bandwidth can be adjusted, but that is in addition to other > filters designed to remove aliases based on the sample rate. > > > On Dec 29, 2017 11:57 AM, "Wahhab Albazrqaoe" <[email protected] > <mailto:[email protected]> <[email protected]>> wrote: > > Hi John, > My question is about USRP B210, can we use it to set RF bw as 50MHz > and then sample using 2MHz sampling rate? > > Thanks > Wahhab > > On Dec 29, 2017 11:54 AM, "John Shields" <[email protected] > <mailto:[email protected]> <[email protected]>> wrote: > > Hi Wahhab, > As Kyeong had already pointed out, in this configuration, the bw > limiting factor is the daughtercard. For the SBX the bandwidth > is 40 MHz. There are other Ettus products covering the same > frequency range which have wider bandwidth (80,120,160 MHz) but > they seem to only plug into the X-series of products. > https://www.ettus.com/product/category/Daughterboards > <https://www.ettus.com/product/category/Daughterboards> > <https://www.ettus.com/product/category/Daughterboards> > Kind Regards, > John > *From:* Wahhab Albazrqaoe <mailto:[email protected]> > <[email protected]> > *Sent:* Saturday, December 30, 2017 4:39 AM > *To:* Kyeong Su Shin <mailto:[email protected]> <[email protected]> > *Cc:* John Shields <mailto:[email protected]> > <[email protected]> ; > [email protected] <mailto:[email protected]> > <[email protected]> > *Subject:* Re: [USRP-users] Enable aliasing using USRP > Dear Kyeong, > Thank you for the reply. > How about using USRP B210, do you think we can get aliasing by > setting the RF bw=50MHz and sample at 2MHz? > Thank you. > Wahhab > On Dec 29, 2017 12:19 AM, "Kyeong Su Shin" <[email protected] > <mailto:[email protected]> <[email protected]>> wrote: > > Hello Wahhab, > If I recall correctly, you can *not* change the bandwidth of > SBX (always 40MHz), and the sampling rate of the USRP2 > (always 100MS/s). What you are actually setting by setting > --rate 2e6 is the decimation ratio. The signals will be > always sampled at 100MS/s, and then decimated by the > decimator within the FPGA. > It is still possible to cause aliasing - one way is to just > sample at a fast sampling rate and then decimate by > yourself. An other way would be tinkering the digital > filters used by the decimator, but I am not sure if there > are good APIs to do that. I am pretty sure that > rx_samples_to_file is not suitable for the task, though > (correct me if I am wrong). That is just an example program. > Regards, > Kyeong Su Shin > On Thu, Dec 28, 2017 at 6:29 PM, Wahhab Albazrqaoe via > USRP-users <[email protected] > <mailto:[email protected]> > <[email protected]>> wrote: > > Hi John, > Thank you for your reply. > We would like to create aliasing. This means that we > should set ADC to sample at speed less than Nyquist rate. > In our setting, we target RF front end to be 50MHz and > ADC speed is 2MHz. > The question is how to do it? We use some commands (as > shown in my previous email) but seems not working as > expected, i.e. RF front end bandwidth is still 2MHz. > Best, > On Thu, Dec 28, 2017 at 9:24 PM, John Shields > <[email protected] > <mailto:[email protected]> <[email protected]>> > wrote: > > Hi Wahhab, > This is a fairly basic issue – the ‘bandwidth’ (if > that is really what you are really meaning) is > related to the sample_rate by The Nyquist Frequency > https://en.wikipedia.org/wiki/Nyquist_frequency > <https://en.wikipedia.org/wiki/Nyquist_frequency> > <https://en.wikipedia.org/wiki/Nyquist_frequency> > Kind Regards, > John > *From:* Wahhab Albazrqaoe via USRP-users > <mailto:[email protected]> > <[email protected]> > *Sent:* Friday, December 29, 2017 3:04 PM > *To:* [email protected] > <mailto:[email protected]> > <[email protected]> > *Subject:* [USRP-users] Enable aliasing using USRP > Dear All, > I have question about how to create aliasing using > USRP. > Basically, I have USRP2 with SBX (with recent > installations of GnuRadio and UHD). > I would like to set the bandwidth of the RF front > end to 50 MHz, and use 2MHz of sampling rate (ADC > speed). > I am using the following command: > sudo ./rx_samples_to_file --args addr=192.168.10.2 > master_clock_rate=50e6 --freq=2460e6 --bw=50e6 > --rate 2e6 --gain=50 --wirefmt sc8 --nsamps 0 > Problem: it seems to me that the system > (GnuRadio/USRP) observes only 2MHz of RF front end > bandwdith. How do I know this? Ans: I compare such > settings with the following settings: > sudo ./rx_samples_to_file --args addr=192.168.10.2 > master_clock_rate=50e6 --freq=2460e6 --bw=50e6 > --rate 50e6 --gain=50 --wirefmt sc8 --nsamps 0 > The later setting seems to be actual 50 MHz of Rf > front end. > Any comments and advices on how to create aliasing > using USRP are appreciate. > Best, > Wahhab > ------------------------------ > ------------------------------------------ > _______________________________________________ > USRP-users mailing list > [email protected] > <mailto:[email protected]> > <[email protected]> > http://lists.ettus.com/mailman/listinfo/usrp-users_ > lists.ettus.com > <http://lists.ettus.com/mailman/listinfo/usrp-users_ > lists.ettus.com> > <http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com> > > <https://www.avast.com/sig-email?utm_medium=email&utm_ > source=link&utm_campaign=sig-email&utm_content=emailclient> > <https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=emailclient> > Virus-free. www.avast.com > <https://www.avast.com/sig-email?utm_medium=email&utm_ > source=link&utm_campaign=sig-email&utm_content=emailclient> > <https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=emailclient> > > > > _______________________________________________ > USRP-users mailing list > [email protected] > <mailto:[email protected]> > <[email protected]> > http://lists.ettus.com/mailman/listinfo/usrp-users_ > lists.ettus.com > <http://lists.ettus.com/mailman/listinfo/usrp-users_ > lists.ettus.com> > <http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com> > > > > _______________________________________________ > USRP-users mailing list > [email protected] > http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com > > > > _______________________________________________ > USRP-users mailing list > [email protected] > http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com > > > _______________________________________________ > USRP-users mailing list > [email protected] > http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com > > >
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