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 >> >> <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]> <mailto:[email protected]> >>> <mailto:[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]> >>> <mailto:[email protected]> <mailto:[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> >>> <https://www.ettus.com/product/category/Daughterboards> >>> Kind Regards, >>> John >>> *From:* Wahhab Albazrqaoe <mailto:[email protected]> >>> <mailto:[email protected]> >>> *Sent:* Saturday, December 30, 2017 4:39 AM >>> *To:* Kyeong Su Shin <mailto:[email protected]> <mailto:[email protected]> >>> *Cc:* John Shields <mailto:[email protected]> >>> <mailto:[email protected]> ; >>> [email protected] <mailto:[email protected]> >>> <mailto:[email protected]> <mailto:[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]> >>> <mailto:[email protected]> <mailto:[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]> >>> <mailto:[email protected]> >>> <mailto:[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]> >>> <mailto:[email protected]> >>> <mailto:[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> >>> <https://en.wikipedia.org/wiki/Nyquist_frequency> >>> Kind Regards, >>> John >>> *From:* Wahhab Albazrqaoe via USRP-users >>> <mailto:[email protected]> >>> <mailto:[email protected]> >>> *Sent:* Friday, December 29, 2017 3:04 PM >>> *To:* [email protected] >>> <mailto:[email protected]> >>> <mailto:[email protected]> >>> <mailto:[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]> >>> <mailto:[email protected]> >>> <mailto:[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> >>> <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 <http://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]> >>> <mailto:[email protected]> >>> <mailto:[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> >>> <http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com> >>> >>> >>> >>> _______________________________________________ >>> USRP-users mailing list >>> [email protected] <mailto:[email protected]> >>> 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] <mailto:[email protected]> >> 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
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