Re: ETTUS N210 spurious

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
>>
>>
>