We are using the 1305 AD converter and driving it with a 20MHz clock we could se a ripple on the output signal after sinc 3 filter and down sampling to 100kHz of 12.5kHz. we analyzed the output signal from the 1305
and could see a nose with the frequency of ~312 kHz. this mirrowed with 100kHz will be ~12kHz. Now is the question, were do you think the origin of the 312kHz noise on the output signal comes from.(20M/312.5 is 64)
From 1305 bitstream:
Filtered and down sampled signal :
