Hi Snehasish, knowing the roll-off of the halfband filters in the USRP, this is rather surprising. So, my best guess is that there's might be a problem with your software, but I can't really assess that.
Best regards, Marcus On 09/13/2017 12:41 PM, Snehasish Kar via USRP-users wrote: I have noticed that IQ will stream from unpopulated daughtercard slots... Is this expected? > Hi, > > > I am capturing 75 MHz using 100 MSps sample rate as well as using 200 > MSps sample rate but I am not getting the near-end bands with 100 MSps > while I am getting those with 200 MSps. What I have done is capture > the data and then pass it through a polyphase channelizer to give me > 200 K bandwidth channels and then I am upsampling that data to 1 MSps > or 2 Msps and passing through gr-gsm receiver. With 200 MSps I am > getting correct data whereas with 100 MSps I am not. But according to > usrp specs my sampling rate as 1.25*75 MHz should be enough but that > is not happening. Please help. > > > Regards, > > Snehasish > > ------------------------------------------------------------------------ > *From:* Derek Kozel <derek.ko...@ettus.com> > *Sent:* Wednesday, August 23, 2017 12:15:11 PM > *To:* Koyel Das > *Cc:* Snehasish Kar; usrp-users@lists.ettus.com > *Subject:* Re: [USRP-users] Support with setting usrp sampling rate to > 150MSPS > > Hello Koyel, > > This is a fundamental problem that increasing sample rate takes more > processing power to handle but provides more bandwidth of spectrum. > How wide is the signal you need to process? The general recommendation > is that you sample at 1.25 times your bandwidth. This provides 20% > more spectrum than is necessary, but means that your signal is > minimally affected by the digital filters used in the decimation in > the FPGA. This is part of how the 160 MHz bandwidth of the UBX is > derived from the 200 MHz sampling rate of an X310 (what is inside the > 2954R). > > The default FPGA image is limited to integer decimation rates as > described in the manual. > http://files.ettus.com/manual/page_general.html#general_sampleratenotes > > GSM 1800 covers 170 MHz so even with the full sampling rate the > outermost edges will be attenuated by both the analog filters and the > digital filters. If you only want to look at the uplink or downlink > individually then you can observe the 75 MHz bandwidth with 100 MS/s > and easily meet the recommended maximum of 80% occupied bandwidth. > > For non-integer decimation rates such as 200e6/150e6 = 4/3 you would > have to implement a rational resampler as a custom RFNoC block to > support that decimation rate, certainly possible but additional work. > > Regards, > Derek > > On Wed, Aug 23, 2017 at 7:17 AM, Koyel Das <koyel....@vehere.com > <mailto:koyel....@vehere.com>> wrote: > > Hi, > > Many thanks for your reply. Yes 200 MSps works. > > But taking 200 MSps will increase the amount of data considerably > and increase the processing time and very less amount of data is > decoded from large amount of input samples compared to lower > sampling frequencies. What is the solution to these problems? > > Regards, > Koyel > > On Tue, Aug 22, 2017 at 9:14 PM, Snehasish Kar > <snehasish....@live.com <mailto:snehasish....@live.com>> wrote: > > Ok I will try that. > > BR > Snehasish > > On 22-Aug-2017, at 8:51 PM, Derek Kozel <derek.ko...@ettus.com > <mailto:derek.ko...@ettus.com>> wrote: > >> Try 200MS/s. The FPGA can only decimate integer amounts from >> the ADC rate, which is 200MS/s. >> >> On Tue, Aug 22, 2017 at 5:15 PM, Snehasish Kar via USRP-users >> <usrp-users@lists.ettus.com >> <mailto:usrp-users@lists.ettus.com>> wrote: >> >> Hello >> I am trying to receive gsm 1800 band using NI USRP 2954R, >> but when I am trying to set the sampling rate of >> uhd_source in gnuradio to 150 MSPS, it's giving an error >> message saying hardware does not support sampling rate >> above 100MSPS. >> >> Please help! >> >> BR >> Snehasish >> _______________________________________________ >> USRP-users mailing list >> USRP-users@lists.ettus.com >> <mailto: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> >> >> > > > > -- > > Koyel Das > > Senior Product Engineer > > Vehere | Proactive Communications Intelligence & Cyber Defence > > M: +919051132173 <tel:+91%2090511%2032173> | T: +91 33 24008400 > <tel:+91%2033%202400%208400> | F: +91 33 247988100 | W: > www.vehere.com <http://www.vehere.com> > > > Vehere is the proud recipient of the Fastest Growing Technology > Company Awards in India & Asia since 2012! > > > The content of this e-mail is confidential and intended solely for > the use of the addressee. 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