Hello Ben:
USRP N210 samples at 100MS/s (with an additional 4x interpolation in case of Tx - making it 400MS/s). The maximum effective sampling rate, however, is bottlenecked by the connection between the USRP and the PC. The 1Gbps Ethernet connection can keep up with a 25MS/s 16bit I-Q data stream or a 50MS/s 8bit I-Q data stream. Faster rate will cause a data loss. What is important is that the internal sampling rate of the USRP N210 is fixed. It is always 100MS/s. When you set the effective sampling rate (which is different from the internal sampling rate of the ADC and DAC) of the USRP in your code, the data is transferred to the USRP at the configured rate and then resampled by the FPGA of the USRP to meet the ADC/DAC sampling rate (100MS/s). This resampler(interpolator) has several restrictions, and restrics the valid choice of the effective sampling rate (the sampling rate that you are setting in your software). That is what Marcus explained in the previous e-mail. So, yes, you can get 50MS/s from your board, but the precision of the data should be 8 bit instead of 16 bit (which is usually not a good idea). Furthermore, this does not concern the analog filters installed on the daughterboard, which may further reduce the usable bandwidth. Also, yes, at N=200, the effective sampling rate of the board is 500kS/s and that should work without a problem. Regards, Kyeong Su Shin ________________________________ 보낸 사람: Benny Alexandar via USRP-users <[email protected]> 대신 USRP-users <[email protected]> 보낸 날짜: 2018년 3월 24일 토요일 오후 2:32:24 받는 사람: Marcus Müller via USRP-users; Marcus D. Leech; Marcus Müller 제목: Re: [USRP-users] IQ transmission using grc Hi Marcus, I'm not clear on maximum sample rate support for USRP N210. According to you >> In case of the N210, these frequencies are integer fractions of 100 MHz >> i.e. 100 MHz / N, with the restriction that N be an integer 3 < n <= >> 128 , an even integer 2 < n <= 256 or an integer multiple of 4 <= 512. Assume I use N an even minimum integer say 2, then the sampling frequency I can get on USRP N210 is 100 MHz / 2 = 50 MHz. Is that correct ? Can USRP sample at such high rates ? If I need a bandwidth of say 500kHz, from USRP then I need to set N = 200, is my math correct and the sample rates to set for usrp ? -ben ________________________________ From: USRP-users <[email protected]> on behalf of Marcus Müller via USRP-users <[email protected]> Sent: Wednesday, March 21, 2018 2:10 AM To: Marcus D. Leech; [email protected] Subject: Re: [USRP-users] IQ transmission using grc Hi ben, also, no USRP can directly deal with a sampling rate as low as 48 kHz – you'll first have to resample to a rate that your USRP can deal with. In case of the N210, these frequencies are integer fractions of 100 MHz i.e. 100 MHz / N, with the restriction that N be an integer 3 < n <= 128 , an even integer 2 < n <= 256 or an integer multiple of 4 <= 512. tx_samples_from_file can't resample – you should have been getting UHD warnings about impossible sampling rates; your IQ file has simply been played back at a higher rate. Best regards, Marcus On Tue, 2018-03-20 at 12:58 -0400, Marcus D. Leech via USRP-users wrote: > On 03/20/2018 12:37 PM, Benny Alexandar via USRP-users wrote: > > Hi, > > > > I have an IQ file sampled at 48kHz and want to transmit through gnu > > radio. The IQ samples are each 16bit, and stored interleaved in a > > file > > ie, IQIQIQIQ... I 16 bit and Q 16bit > > > > I tried creating a grc using iShort to Complex block and send to > > USRP sink block (usrp n210), but the signal received is distorted. > > Do I need to convert the short values into float -1.0 to +1.0 > > before transmission. Please help in resolving it. > > > > I want to use it only through grc and not to use > > tx_samples_from_file which does the same. > > > > -ben > > > You'll need to scale your samples into {-1.0,1.0} > > > > _______________________________________________ > 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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