SNR Degradation due to CIC Filter

[Eminent.Engineer]

Hello Everyone,

Delta Sigma ADC:
Modulator = 2nd Order
CIC Filter = 3rd Order
OSR = 256

CIC is hardware efficient Decimation Filter but its frequency response shows passband droop and wide transition band, so my question is due to these non-idealities of CIC filter, How much degradation in SNR occur and theory about estimating this degradation ?

Thanks in Advance.

 

[FvM]

I see two ways to downgrade SNR with unsuitable designed decimation:
- bit width too low (generating quantization noise)
- alias frequency suppression too low (insuffcient filter order related to the application)

With correct designed decimation, there's no significant SNR degradation