Hi Abhinav, which USRP are you using? I'm pretty sure none of our devices supports a 2kS/s sampling rate -- it's just far too low to get directly interpolated to a "usable" DAC/ADC rate. Especially those USRPs that can be equipped with RF frontends (daughterboards) that can operate at near-baseband (400kHz) shouldn't be able to work at such low rates. So: which daughterboard are you using?
Hence, UHD should have told you that you can't use that sampling rate, and a higher sampling rate was automatically selected, inherently frequency-"stretching" the signal by the ratio of (actual rate/2kHz). You should heed Sylvain's advice. Just oversample your signal by using an interpolating FIR filter to something that the USRP can happily work with. Best regards, Marcus On 21.10.2015 08:49, abhinav narain wrote: > Hi, > I am transmitting using the flowgraph: vector src-> FIR interpolator > (with RRC filter as below) -> MultiplyConst -> USRP Block > > FIR filter - firdes.root_raised_cosine(32, samp_rate, sps, 0.55, > int(11*sps*32)), with > center freq= 400kHz > samp_rate= 1k > > I am listening using other USRP with > center freq= 400kHz > samp_rate= 2k > > > You can see the spectrogram at the receiver. I want to do narrowband(1 > kHz) transmission hence I am keeping the sampling freq at transmitter > at 1k. > > While I increase the signal amplitude(using MultiplyConst block with > slider), I see there is more and more spillage of energy in the > neighboring frequencies! > > Is there a way to remove that spillage from the transmitter and have a > cleaner transmitter ? > If not, how can I atleast mitigate it to the minimum ? is there > something I can do with RRC filter parameter or any other way ? > > In the figure: 1 - when amplitude is large; 2 - when amplitude is > turned down > > Thanks, > Abhinav > > > _______________________________________________ > Discuss-gnuradio mailing list > Discuss-gnuradio@gnu.org > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
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