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SINC response in ADC

Category: Hardware
Product Number: AD9697

I plan to sample 290-380M using AD9695-625 ADC with a 400M input clock. The decimation rate is 8, so so the JESD output rate is 2Gbps. I will use the NCO freq to tune within290-380M; the instantaneous bandwidth is < 5MHz.

1) Simulating with the VIRTUAL Eval tool - BETA, I see no apparent drop off with RF input from 290-390M. Is this real?  Because I would sinx/x (SINC) effects to have an impact.

2) The FFT output is -7dBFS for a -1dBFS input setting. Why the 6dB loss? Is the simulation assuming such a loss in input matching ??

3) Screen shot below shows RF =393M (out-of-band) causing a spur  -22M. Since 0Hz maps to NCO freq =379M, the main tone = (RF in -NCO) = 393-379 = 14M. -22M spur is equivalent to 379-22= 357M. What causing this ??

Top Replies

  • Hi  ,

    Thanks for your interest in AD9695.

    I acknowledged your query and will ping the product owner for more detailed answer. 

    For question no.2, the -6dB loss is due to DDC NCO + mixer loss as…