Hello,
Thanks for the reply. As I wrote, I try several sampling rate on the
baseband I provide to the USRP without any effects on that spurs so it
is not related to the sampling rate. I just put a signal source that
feeds the USRP sink for that test.
It should be EMC related, as far as I understand reading all answer on
that mailing list.
Thanks,
Best regards,
Fabien, F4CTZ.
Le 01/02/2022 à 12:12, Steve Hubbard a écrit :
Sorry for the late reply. I am guessing you are seeing aliases of the
audio signal. Sampling a 1 kHz signal at 32 kHz produces aliases
around multiples of the 32 kHz. In the signal processing chain the
sampling rate will be increased in stages until the DAC sampling rate
is reached. This process of interpolation involves inserting zero
valued samples between the existing samples and then applying a
digital low pass filter to attenuate the aliases. The stop band of the
filter may be -70 dB so low level spurii remain. -70 dB is low enough
for most intents and purposes and probably doesn't need fixing.
Steve
On 19/1/22 1:31 am, Fabien PELLET wrote:
Hello,
When I put a signal generator that produces a sinwave at 1Khz and
that feeds an USRP Sink with a frequency center at 12MHz for example,
I got spurs at +/-32Khz, +/-64KHz and +/-96KHz at the output of my
N210 (used with LFTX and LFRX). Whatever the frequency center of the
USRP and the frequency of the baseband signal, I have to spurs around
-70dBc.
Any idea on where it could come from ? Hardware EMC problem ? Digital
treatment issue ? How to solve it ?
Best regards,
Fabien, F4CTZ
