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
