Hello, You are receiving the maximum possible sample rate. The TwinRX is able to provide two channels of data compared to the usual 1 per daughterboard because it uses the 200 MS/s ADC to do real mode sampling on the two channels. The FPGA then does a conversion to 100 MS/s Complex samples for each of the two channels since all the rest of the DSP chain is designed for complex signals. There is no way to bypass this real to complex conversion in the prebuilt FPGA images.
The TwinRX only supports the use of the 200 MHz master clock rate. The IF passband filter provides 80 MHz of bandwidth per channel which follows the general convention of usable bandwidth being 80% of the sample rate when using complex samples. If the sample rate is reduced below 200 MS/s real (100 MS/s complex) then that IF filtering is insufficient and aliasing will occur. Additionally the IP for doing the final conversion to baseband is based on having that full bandwidth available. Regards, Derek On Fri, Mar 2, 2018 at 2:57 PM, Андрей 1 via USRP-users < usrp-users@lists.ettus.com> wrote: > I right now started benchmark_rate with sample rate 200 but got 100 > MHz(see png). > Can I get data without decimation on a clock 200 MHz? > > Thank you. > > 02.03.2018, 16:30, Daniel Jepson <daniel.jep...@ettus.com> > Hi, > > The X300/X310 supports three Sampling Rates: 120MHz, 184.32MHz, and > 200MHz. Your rate was most likely coerced to the most common rate of 200M. > The FPGA then performs decimation and interpolation such that the host > doesn't have to stream all that bandwidth (nor can it in most cases). The > streaming rate called out in your screen shots is 10.0Msps. > > Does that answer your question? > > -Daniel > > On Fri, Mar 2, 2018 at 7:57 AM, Андрей 1 via USRP-users < > usrp-users@lists.ettus.com> wrote: > > > Hello > > When I open device with uhd_usrp_make in the terminal I see a message > "invalid sample rate 100 MHz actual rate is 200 MHz".The same message I see > when running application from uhd samples folder. > If I set sample rate 200 MHz and then read them from device I got 100 MHz. > > What does this mean and what is the maximum clock of the X300 in single > and multichannel mode? > > See png for detail. > > Thank you > > _______________________________________________ > USRP-users mailing list > USRP-users@lists.ettus.com <usrp-users@lists.ettus.com> > http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com > > > > > -- > > Daniel Jepson > > Digital Hardware Engineer > > National Instruments > > > > O: +1.512.683.6163 <(512)%20683-6163> > > daniel.jep...@ni.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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