On 10/18/2018 09:44 AM, Mercado, Alejandra via USRP-users wrote:
Thanks for your response and please, forgive the delay in responding.
I recorded the different sampling rates and the warnings that
sometimes appeared for some sampling rates.
For example, when I set samp_rate=960kHz, it gave this message:
** UHD Warning:
The requested decimation is odd; the user should expect CIC rolloff.
Select an even decimation to ensure that a halfband filter is enabled.
decimation = dsp_rate/samp_rate -> 65 = (58.880000 MHz)/(0.910000 MHz)
But, on the other hand, when I set samp_rate= 650 kHz -- that is to
say, then the noise level doe NOT take a 20 dB jump -- it gave me the
same message:
** UHD Warning:
The requested decimation is odd; the user should expect CIC rolloff.
Select an even decimation to ensure that a halfband filter is enabled.
decimation = dsp_rate/samp_rate -> 65 = (41.600000 MHz)/(0.640000 MHz)
In both cases I warned about CIC roll-off, but one of them has the
20dB jump and the other does not.
As per your instructions, I checked a "bad" one surrounded by two
"good" ones:
Trial 1:
samp_rate=110kHz Average_noise=-83dBFS asking_clock_rate=56.32MHz &
samp_rate=120kHz Average_noise=-67dBFS asking_clock_rate=61.44MHz&
samp_rate=130kHz Average_noise=-82dBFS asking_clock_rate=33.22MHz
no warnings about sampling rate in any of the three
Trial 2:
samp_rate=220kHz Average_noise=-82dBFS asking_clock_rate=56.32MHz &
samp_rate=240kHz Average_noise=-64dBFS asking_clock_rate=61.44MHz &
samp_rate=250kHz Average_noise=-81dBFS asking_clock_rate=32MHz
Only one message showed up for samp_rate=250kHz (which does not suffer
20dB jump):
** UHD Error:
recv packet demuxer unexpected sid 0x20020a0
D
Any ideas?
Thanks again for your time.
Regards
It would be very useful to look at the FFTs (spectrum) of the band when
selecting the "bad" sample rates. You're mostly looking at internal
noise under the conditions you describe (shorted antenna input, and
0dB gain).
_______________________________________________
USRP-users mailing list
USRP-users@lists.ettus.com
http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
