Re: aliasing with X310 BasicRX (higher order Nyquist zone) ?

Indeed second Nyquist zone before decimation.
My thought was
143.05 MHz -> transpose by 100 MHz using the DDC (NCO at 100 MHz considering the
200 MHz sampling rate) to reach 43.05, and after transposition, decimating to reach
8 MS/s (I do have Epcos B3607 SAW filters 140+/-3 MHz frontend to select only the
signal I am interested in).
It is in the decimation process that I was thinking of being in the third
Nyquist zone after decimation, which is incorrect because 8 MS/s is -4 to +4, so that
43.05 is in the 6th Nyquist zone after decimation (\in[36:44] MHz).

Thanks, JM

--
JM Friedt, FEMTO-ST Time & Frequency/SENSeOR, 26 rue de l'Epitaphe,
25000 Besancon, France

July 20, 2020 5:20 PM, "Marcus D. Leech" <patchvonbraun@gmail.com> wrote:

> On 07/20/2020 07:37 AM, jean-michel.friedt@femto-st.fr wrote:
>
>> I'd like to analyze a higher Nyquist zone with a X310 fitted with a BasicRX:
>> trying to listen at 143.5 MHz (GRAVES), I can transpose by 100 MHz but am still
>> far from the ~8 MS/s sampling I can use on the Gb Ethernet interface. Since the
>> signal is only in the third Nyquist zone, I'd like to tell the BasicRX/DDC *not*
>> to anti-alias (CIC filter ?) the received signal. It tried playing with the
>> Bandwidth parameter of the USRP Sink but no improvement there.
>>
>> Is there a way to alias on purpose the signal with X310+BasicRX ?
>>
>> Thanks, JM
>>
>> --
>> JM Friedt, FEMTO-ST Time & Frequency/SENSeOR, 26 rue de l'Epitaphe,
>> 25000 Besancon, France
>
> The X310 has a 200MHz ADC clock by default, so 143.5MHz would be in the 2nd Nyquist zone, would it
> not?